Operations with multi-digit numbers

First find how many full boxes remain. Multiply that number by the quantity per box.

The library received books twice. Add the two amounts to find the total number of new books.

Line up the ones, tens and hundreds. Find the total received, rather than the difference between the deliveries.

Find each delivery’s pencil count with a separate multiplication, then add the two products.

Read the operation sign first.

• For addition or subtraction, work with ones, tens and hundreds. Regroup when needed: 10 ones = 1 ten.
• For multiplication, split a number: 6 × 24 = 6 × 20 + 6 × 4.
• Check division by multiplying: result × divisor must give the starting number.

Multiply the box count by the quantity per box, then subtract the distributed quantity.

Find the cost of one kit including its packing. Multiply that sum by the number of kits.

Use long division or split the dividend into convenient parts.

For example, 168 ÷ 7 = 140 ÷ 7 + 28 ÷ 7 = 20 + 4 = 24. Check that result × divisor gives the starting number.

Sending boxes away leaves fewer boxes. Subtract the number sent away from the starting number.

Check: the boxes left and the boxes sent away must add up to the starting amount.

Find the missing addend by subtracting the known addend from the total.

For example, for 240 + ? = 560, the missing amount is 560 − 240 = 320. Check that the known and found addends make the given total.

Line up the ones, tens and hundreds. Add starting with the ones.

If a place adds to 10 or more, carry a ten to the next place. For example, 268 + 157 = 425. Check by subtracting one addend from the result.