Primary 2 Mathematics Addition Subtraction Quiz

Answer Key - Primary 2 Mathematics Quiz - Addition Subtraction

Total Marks: 50 | Duration: 60 minutes

Teaching note for students: When adding, we start from the ones place on the right and move left, carrying over when a column reaches 10 or more. When subtracting, we start from the ones place too, and we borrow (regroup) from the next column when the top digit is too small.

Answer 1.

Answer: 377 (1 mark)

• Ones: $5 + 2 = 7$
• Tens: $4 + 3 = 7$
• Hundreds: $2 + 1 = 3$

No regrouping is needed because no column reaches 10. Common mistake: adding the columns in the wrong order or misaligning the digits.

Answer 2.

Answer: 242 (1 mark)

• Ones: $9 - 7 = 2$
• Tens: $8 - 4 = 4$
• Hundreds: $5 - 3 = 2$

No borrowing is needed. Always check that the top number in each column is bigger than the bottom number before subtracting.

Answer 3.

Answer: 630 (1 mark)

Adding 200 means adding 2 hundreds: 4 hundreds $+$ 2 hundreds $=$ 6 hundreds. The tens and ones stay the same, so $430 + 200 = 630$. This is mental addition of hundreds.

Answer 4.

Answer: 518 (1 mark)

Subtracting 60 means taking away 6 tens: 7 tens $-$ 6 tens $=$ 1 ten. The hundreds and ones stay the same, so $578 - 60 = 518$. Watch out: the ones digit does not change.

Answer 5.

Answer: 60 (1 mark)

The missing number is what we add to 250 to reach 310. Count on from 250 to 310: that is 6 tens, so the missing number is 60. Check: $250 + 60 = 310$. This is the idea of a missing addend, which uses subtraction: $310 - 250 = 60$.

Answer 6.

Answer: 625 (2 marks)

Column addition with regrouping:

• Ones: $8 + 7 = 15$. Write 5, carry 1 to the tens.
• Tens: $5 + 6 + 1 = 12$. Write 2, carry 1 to the hundreds.
• Hundreds: $3 + 2 + 1 = 6$.

So $358 + 267 = 625$.

Marking: M1 for correct column set-up with carries shown or attempted, A1 for correct final answer 625. Common mistake: forgetting to add the carried 1 in the tens column.

Answer 7.

Answer: 338 (2 marks)

Column subtraction with borrowing:

• Ones: $3 - 5$ cannot be done, so borrow 1 ten: $13 - 5 = 8$.
• Tens: after lending, 1 remains; $1 - 8$ cannot be done, so borrow 1 hundred: $11 - 8 = 3$.
• Hundreds: after lending, 5 remains; $5 - 2 = 3$.

So $623 - 285 = 338$.

Marking: M1 for correct borrowing shown, A1 for correct answer 338. Common mistake: subtracting the smaller digit from the larger digit instead of borrowing.

Answer 8.

Answer: 225 (2 marks)

We need the number that makes 400 when added to 175. This is a missing addend, so subtract: $400 - 175 = 225$.

• Ones: $0 - 5$ cannot be done, borrow: $10 - 5 = 5$.
• Tens: $9 - 7 = 2$ (after borrowing).
• Hundreds: $3 - 1 = 2$ (after borrowing).

Check by adding back: $225 + 175 = 400$. Correct.

Marking: M1 for using subtraction or counting-on correctly, A1 for 225.

Answer 9.

Answer: 545 (2 marks)

• $346 + 200 = 546$
• $546 - 1 = 545$

Why this works: 199 is exactly 1 less than 200, so adding 199 gives an answer 1 less than adding 200. This is a mental strategy called compensation.

Marking: M1 for $346 + 200 = 546$, A1 for final answer 545. Common mistake: adding 200 and forgetting to subtract the 1.

Answer 10.

Answer: $<$ (2 marks)

• Left side: $700 - 250 = 450$.
• Right side: 460.
• Compare: $450 < 460$, so the correct sign is $<$.

Marking: M1 for working out $700 - 250 = 450$, A1 for choosing $<$. Common mistake: writing $>$ because 700 looks bigger than 460 without doing the subtraction first.

Answer 11.

Answer: 636 (3 marks)

Subtracting from 1000 needs borrowing across two zeros:

• Ones: $0 - 4$ cannot be done. Borrow from the hundreds through the tens: the thousands-hundreds become 9 hundreds, the tens become 9 tens, and the ones become 10.
• Ones: $10 - 4 = 6$.
• Tens: $9 - 6 = 3$.
• Hundreds: $9 - 3 = 6$.

So $1000 - 364 = 636$.

Quick check method: $999 - 364 = 635$, then add back the 1 we removed: $635 + 1 = 636$.

Marking: M1 for setting up the borrowing across zeros, M1 for correct column subtractions, A1 for 636. Common mistake: writing 746 by skipping the borrowing in the tens column.

Answer 12.

Answer: 682 (3 marks)

Add two numbers first, then add the third:

• $128 + 245$: ones $8+5=13$ (write 3, carry 1); tens $2+4+1=7$; hundreds $1+2=3$. So $128 + 245 = 373$.
• $373 + 309$: ones $3+9=12$ (write 2, carry 1); tens $7+0+1=8$; hundreds $3+3=6$. So $373 + 309 = 682$.

Marking: M1 for first partial sum 373, M1 for second addition set-up, A1 for final answer 682. Common mistake: adding all the digits in one go instead of adding two numbers at a time.

Answer 13.

Answer: The missing digit is 5 (3 marks)

Reasoning step by step:

• Ones: $4 + 6 = 10$. Write 0, carry 1 to the tens. This matches the 0 in 510.
• Tens: the missing digit $+$ 5 $+$ 1 (carry) must end in 1. Try 5: $5 + 5 + 1 = 11$. Write 1, carry 1 to the hundreds. This matches the 1 in 510.
• Hundreds: $3 + 1 + 1$ (carry) $= 5$. This matches the 5 in 510.

Every column checks out, so the missing digit is 5: $354 + 156 = 510$.

Marking: M1 for handling the ones column and carry, M1 for testing the tens column logically, A1 for digit 5 with a valid reason. Accept counting-on or trial-and-error with checking.

Answer 14.

Answer: 382 stickers (3 marks)

Two steps in order:

• Step 1 (giving away means subtract): $465 - 178 = 287$ stickers left.
• Step 2 (buying more means add): $287 + 95 = 382$ stickers.

She has 382 stickers now.

Marking: M1 for $465 - 178 = 287$, M1 for $287 + 95 = 382$, A1 for 382 with units. Common mistake: adding 178 instead of subtracting it, or stopping after the first step.

Answer 15.

Answer: 625 (3 marks)

Follow the path in order:

• Start: 800.
• Subtract 250: $800 - 250 = 550$.
• Add 75: $550 + 75 = 625$.

You land on 625.

Marking: M1 for $800 - 250 = 550$, M1 for $550 + 75 = 625$, A1 for 625. Common mistake: doing the steps in the wrong order, which would give a different landing number.

Answer 16.

Answer: 650 bowls (4 marks)

Altogether means we add all three days:

• $216 + 189$: ones $6+9=15$ (write 5, carry 1); tens $1+8+1=10$ (write 0, carry 1); hundreds $2+1+1=4$. So $216 + 189 = 405$.
• $405 + 245$: ones $5+5=10$ (write 0, carry 1); tens $0+4+1=5$; hundreds $4+2=6$. So $405 + 245 = 650$.

Mr Lim sold 650 bowls of noodles altogether.

Marking: M1 for first addition, M1 for second addition, A1 for correct total 650, A1 for units (bowls) or a complete answer statement. Common mistake: misreading the double carry in $

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Answer Key - Primary 2 Mathematics Quiz - Addition Subtraction

Total Marks: 50 | Duration: 60 minutes

Teaching note: When adding, start from the ones place and carry over when a column reaches 10 or more. When subtracting, borrow (regroup) from the next column when the top digit is too small.

Answer 1.

Answer: 377 (1 mark)

• Ones: $5 + 2 = 7$
• Tens: $4 + 3 = 7$
• Hundreds: $2 + 1 = 3$

No regrouping needed. Common mistake: misaligning the digits.

Answer 2.

Answer: 242 (1 mark)

• Ones: $9 - 7 = 2$
• Tens: $8 - 4 = 4$
• Hundreds: $5 - 3 = 2$

No borrowing needed. Check that each top digit is bigger than the bottom digit.

Answer 3.

Answer: 630 (1 mark)

Adding 200 means adding 2 hundreds: 4 hundreds $+$ 2 hundreds $=$ 6 hundreds. Tens and ones stay the same, so $430 + 200 = 630$.

Answer 4.

Answer: 518 (1 mark)

Subtracting 60 means taking away 6 tens: 7 tens $-$ 6 tens $=$ 1 ten. Hundreds and ones stay the same, so $578 - 60 = 518$. The ones digit does not change.

Answer 5.

Answer: 60 (1 mark)

Count on from 250 to 310: that is 6 tens, so the missing number is 60. Check: $250 + 60 = 310$. This is a missing addend, found by $310 - 250 = 60$.

Answer 6.

Answer: 625 (2 marks)

Column addition with regrouping:

• Ones: $8 + 7 = 15$. Write 5, carry 1 to the tens.
• Tens: $5 + 6 + 1 = 12$. Write 2, carry 1 to the hundreds.
• Hundreds: $3 + 2 + 1 = 6$.

So $358 + 267 = 625$.

Marking: M1 for correct column set-up with carries shown or attempted, A1 for 625. Common mistake: forgetting to add the carried 1 in the tens column.

Answer 7.

Answer: 338 (2 marks)

Column subtraction with borrowing:

• Ones: $3 - 5$ cannot be done, so borrow 1 ten: $13 - 5 = 8$.
• Tens: after lending, 1 remains; $1 - 8$ cannot be done, so borrow 1 hundred: $11 - 8 = 3$.
• Hundreds: after lending, 5 remains; $5 - 2 = 3$.

So $623 - 285 = 338$.

Marking: M1 for correct borrowing shown, A1 for 338. Common mistake: subtracting the smaller digit from the larger instead of borrowing.

Answer 8.

Answer: 225 (2 marks)

This is a missing addend, so subtract: $400 - 175 = 225$.

• Ones: $0 - 5$ cannot be done, borrow: $10 - 5 = 5$.
• Tens: $9 - 7 = 2$ (after borrowing).
• Hundreds: $3 - 1 = 2$ (after borrowing).

Check by adding back: $225 + 175 = 400$. Correct.

Marking: M1 for using subtraction or counting-on correctly, A1 for 225.

Answer 9.

Answer: 545 (2 marks)

• $346 + 200 = 546$
• $546 - 1 = 545$

Why this works: 199 is exactly 1 less than 200, so adding 199 gives an answer 1 less than adding 200. This mental strategy is called compensation.

Marking: M1 for $346 + 200 = 546$, A1 for 545. Common mistake: adding 200 and forgetting to subtract the 1.

Answer 10.

Answer: $<$ (2 marks)

• Left side: $700 - 250 = 450$.
• Right side: 460.
• Compare: $450 < 460$, so the correct sign is $<$.

Marking: M1 for working out $700 - 250 = 450$, A1 for choosing $<$. Common mistake: writing $>$ because 700 looks bigger than 460 without doing the subtraction first.

Answer 11.

Answer: 636 (3 marks)

Subtracting from 1000 needs borrowing across two zeros:

• Ones: $0 - 4$ cannot be done. Borrow across the zeros: the hundreds become 9 hundreds, the tens become 9 tens, and the ones become 10.
• Ones: $10 - 4 = 6$.
• Tens: $9 - 6 = 3$.
• Hundreds: $9 - 3 = 6$.

So $1000 - 364 = 636$.

Quick check method: $999 - 364 = 635$, then add back the 1 we removed: $635 + 1 = 636$.

Marking: M1 for setting up borrowing across zeros, M1 for correct column subtractions, A1 for 636. Common mistake: skipping the borrowing in the tens column.

Answer 12.

Answer: 682 (3 marks)

Add two numbers first, then add the third:

• $128 + 245$: ones $8+5=13$ (write 3, carry 1); tens $2+4+1=7$; hundreds $1+2=3$. So $128 + 245 = 373$.
• $373 + 309$: ones $3+9=12$ (write 2, carry 1); tens $7+0+1=8$; hundreds $3+3=6$. So $373 + 309 = 682$.

Marking: M1 for first partial sum 373, M1 for second addition set-up, A1 for 682. Common mistake: adding all digits in one go instead of two numbers at a time.

Answer 13.

Answer: The missing digit is 5 (3 marks)

Reasoning step by step:

• Ones: $4 + 6 = 10$. Write 0, carry 1 to the tens. This matches the 0 in 510.
• Tens: missing digit $+$ 5 $+$ 1 (carry) must end in 1. Try 5: $5 + 5 + 1 = 11$. Write 1, carry 1 to the hundreds. This matches the 1 in 510.
• Hundreds: $3 + 1 + 1$ (carry) $= 5$. This matches the 5 in 510.

Every column checks out, so the missing digit is 5: $354 + 156 = 510$.

Marking: M1 for handling the ones column and carry, M1 for testing the tens column logically, A1 for digit 5 with a valid reason. Accept counting-on or trial-and-error with checking.

Answer 14.

Answer: 382 stickers (3 marks)

Two steps in order:

• Step 1 (giving away means subtract): $465 - 178 = 287$ stickers left.
• Step 2 (buying more means add): $287 + 95 = 382$ stickers.

She has 382 stickers now.

Marking: M1 for $465 - 178 = 287$, M1 for $287 + 95 = 382$, A1 for 382 with units. Common mistake: adding 178 instead of subtracting it, or stopping after the first step.

Answer 15.

Answer: 625 (3 marks)

Follow the path in order:

• Start: 800.
• Subtract 250: $800 - 250 = 550$.
• Add 75: $550 + 75 = 625$.

You land on 625.

Marking: M1 for $800 - 250 = 550$, M1 for $550 + 75 = 625$, A1 for 625. Common mistake: doing the steps in the wrong order.

Answer 16.

Answer: 650 bowls (4 marks)

Altogether means we add all three days:

• $216 + 189$: ones $6+9=15$ (write 5, carry 1); tens $1+8+1=10$ (write 0, carry 1); hundreds $2+1+1=4$. So $216 + 189 = 405$.
• $405 + 245$: ones $5+5=10$ (write 0, carry 1); tens $0+4+1=5$; hundreds $4+2=6$. So $405 + 245 = 650$.

Mr Lim sold 650 bowls of noodles altogether.

Marking: M1 for first addition, M1 for second addition, A1 for correct total 650, A1 for units (bowls) or a complete answer statement. Common mistake: misreading the double carry in the first addition.

Answer 17.

Answer: 127 pupils (4 marks)

"How many more" means subtract:

• Ones: $6 - 9$ cannot be done, borrow 1 ten: $16 - 9 = 7$.
• Tens: after lending, 7 remains; $7 - 5 = 2$.
• Hundreds: $4 - 3 = 1$.

So $486 - 359 = 127$.

Junction Primary School has 127 more pupils than Rivervale Primary School.

Marking: M1 for correct subtraction set-up, M1 for correct borrowing, A1 for 127, A1 for units (pupils) or a complete answer statement. Common mistake: adding the two numbers instead of subtracting.

Answer 18.

Answer: $180 (4 marks)

Two steps in order:

• Step 1 (total spent): \235 + $85$: ones$5+5=10$(write 0, carry 1); tens$3+8+1=12$(write 2, carry 1); hundreds$2+1=3$. Total spent$= $320$.
• Step 2 (money left): \500 - $320$: ones$0-0=0$; tens$0-2$cannot be done, borrow:$10-2=8$; hundreds$4-3=1$. Money left$= $180$.

Ravi has $180 left.

Marking: M1 for finding total spent \320$, M1 for correct subtraction from$$500$, A1 for$$180$, A1 for units ($ or a complete answer statement. Common mistake: forgetting to add both items before subtracting.

Answer 19.

Answer: 190 more children (4 marks)

Two steps in order:

• Step 1 (find the number of children): $720 - 265$: ones $0-5$ cannot be done, borrow: $10-5=5$; tens $1-6$ cannot be done, borrow: $11-6=5$; hundreds $6-2=4$. Children $= 455$.
• Step 2 (find how many more children than adults): $455 - 265$: ones $5-5=0$; tens $5-6$ cannot be done, borrow: $15-6=9$; hundreds $3-2=1$. Difference $= 190$.

There were 190 more children than adults at the concert.

Marking: M1 for finding 455 children, M1 for the comparison subtraction, A1 for 190, A1 for units or a complete answer statement. Common mistake: stopping at 455 without comparing, or subtracting 265 twice incorrectly.

Answer 20.

Answer: 206 apples (4 marks)

Two steps in order:

• Step 1 (total sold): $348 + 296$: ones $8+6=14$ (write 4, carry 1); tens $4+9+1=14$ (write 4, carry 1); hundreds $3+2+1=6$. Total sold $= 644$.
• Step 2 (apples left): $850 - 644$: ones $0-4$ cannot be done, borrow: $10-4=6$; tens $4-4=0$; hundreds $8-6=2$. Apples left $= 206$.

The fruit seller has 206 apples left.

Marking: M1 for finding total sold 644, M1 for correct subtraction from 850, A1 for 206, A1 for units (apples) or a complete answer statement. Common mistake: subtracting only one day's sales, or forgetting the carry in the tens column.

End of Answer Key