Question paper, Set 8

(i) Start at $5$ and count on $4$: $5 + 4 = 9$

(ii) Count back $2$ from $3$: $3 - 2 = 1$

Answer: (i) $9$ (ii) $1$

$9$ needs $1$ to make $10$; take $1$ from $8$, which leaves $7$.

$9 + 8 = 10 + 7 = 17$

Answer: $\square = 7$; $9 + 8 = 17$

$\square = 4 - 1 = 3$

Check: $1 + 3 = 4$

Answer: $3$

(i) $80 = 70 + 10$ and $10 - 7 = 3$, so $80 - 7 = 70 + 3 = 73$

(ii) $90 = 80 + 10$ and $10 - 4 = 6$, so $90 - 4 = 80 + 6 = 86$

Answer: (i) $73$ (ii) $86$

Take $2$ from the units digit: $5 - 2 = 3$; the tens digit $7$ stays.

$75 - 2 = 73$

Answer: $73$

1st method: take $1$ out of $6$ first ($6 - 1 = 5$): $11 - 6 = 10 - 5 = 5$

2nd method: add $4$ to both: $11 - 6 = 15 - 10 = 5$

Both methods give $11 - 6 = 5$

Answer: $5$

1st method: take $3$ out of $8$ first ($8 - 3 = 5$): $43 - 8 = 40 - 5 = 35$

2nd method: add $2$ to both: $43 - 8 = 45 - 10 = 35$

3rd method: $43 - 10 = 33$ and $10 - 8 = 2$, so $43 - 8 = 33 + 2 = 35$

All three methods give $43 - 8 = 35$

Answer: $35$

Take $2$ tens from $8$ tens: $8 - 2 = 6$; the units digit $7$ stays.

$87 - 20 = 67$

Answer: $67$

1st method (take the tens first): $51 - 23 = 31 - 3 = 30 - 2 = 28$

2nd method: add $7$ to both: $51 - 23 = 58 - 30 = 28$

3rd method: $51 - 30 = 21$ and $30 - 23 = 7$, so $51 - 23 = 21 + 7 = 28$

4th method (column): $1 < 3$, so borrow $1$ ten: units $11 - 3 = 8$, tens $4 - 2 = 2$

All four methods give $51 - 23 = 28$

Answer: $28$

(i) $450 = 440 + 10$ and $10 - 8 = 2$, so $450 - 8 = 440 + 2 = 442$

(ii) units $6 - 4 = 2$, tens $9 - 4 = 5$, hundreds $4$ stays: $496 - 44 = 452$

Answer: (i) $442$ (ii) $452$

1st method (take the tens first): $486 - 59 = 436 - 9 = 430 - 3 = 427$

2nd method: add $1$ to both: $486 - 59 = 487 - 60 = 427$

3rd method: $486 - 60 = 426$ and $60 - 59 = 1$, so $486 - 59 = 426 + 1 = 427$

4th method (column): $6 < 9$, so borrow $1$ ten: units $16 - 9 = 7$, tens $7 - 5 = 2$, hundreds $4$

All four methods give $486 - 59 = 427$

Answer: $427$

Take away the tens first: $100 - 20 = 80$

$100 - 28 = 80 - 8 = 72$

Answer: $72$

1st method (column): units $5 < 6$, borrow $1$ ten: $15 - 6 = 9$

tens: $6 < 9$, borrow from the hundred: $16 - 9 = 7$, hundreds $0$

2nd method: take $5$ from both: $175 - 96 = 170 - 91$

take $70$ from both: $= 100 - 21 = 79$

3rd method: $175 - 100 = 75$ and $100 - 96 = 4$, so $175 - 96 = 75 + 4 = 79$

All three methods give $175 - 96 = 79$

Answer: $79$

Add the tens: $50 + 70 = 120$; the units digit $6$ stays.

$50 + 76 = 126$

Answer: $126$

Tens: $30 + 10 = 40$

Units: $3 + 5 = 8$

$33 + 15 = 40 + 8 = 48$

Answer: $48$

$24 \div 9$: $9 \times 2 = 18$, $24 - 18 = 6$

Bring down $4$, we have $64$: $9 \times 7 = 63$, $64 - 63 = 1$

Bring down $8$, we have $18$: $9 \times 2 = 18$, $18 - 18 = 0$

Remainder $0$, so $2448 \div 9 = 272$

Answer: $272$

$39 \div 5$: $5 \times 7 = 35$, $39 - 35 = 4$

Bring down $7$, we have $47$: $5 \times 9 = 45$, $47 - 45 = 2$

Bring down $0$, we have $20$: $5 \times 4 = 20$, $20 - 20 = 0$

Bring down $3$, we have $3$: $3 < 5$, so write $0$ in the quotient

Bring down $1$, we have $31$: $5 \times 6 = 30$, $31 - 30 = 1$

Bring down $0$, we have $10$: $5 \times 2 = 10$, $10 - 10 = 0$

Remainder $0$, so $3970310 \div 5 = 794062$

Answer: $794062$

$9 \div 3$: $3 \times 3 = 9$, $9 - 9 = 0$

Bring down $3$, we have $3$: $3 \times 1 = 3$, $3 - 3 = 0$

Bring down $2$, we have $2$: $2 < 3$, so write $0$ in the quotient

Bring down $1$, we have $21$: $3 \times 7 = 21$, $21 - 21 = 0$

Remainder $0$, so $9321 \div 3 = 3107$

Do not miss the $0$ in the quotient.

Answer: $3107$

$30 \div 12$: $12 \times 2 = 24$, $30 - 24 = 6$

Bring down $8$, we have $68$: $12 \times 5 = 60$, $68 - 60 = 8$

Bring down $4$, we have $84$: $12 \times 7 = 84$, $84 - 84 = 0$

Remainder $0$, so $3084 \div 12 = 257$

Answer: $257$

$\displaystyle \frac{28}{4}$ means $28 \div 4$.

$4 \times 7 = 28$, so $\displaystyle \frac{28}{4} = 7$

Answer: $7$