Review: multiplying, dividing and order of operations
To multiply by 2 digits, find a row for the ones and a row for the tens, with a 0 as place holder, and add the rows. To divide, work from the left: divide, multiply, subtract, bring down; write the remainder and check with quotient × divisor + remainder. Factors are numbers that divide a number exactly, and the greatest common factor is the biggest factor shared by two numbers. Multiples are the numbers in the times table; the first multiple that two numbers share is their lowest common multiple. In expressions, parentheses come first, then multiplication and division, then addition and subtraction from left to right. Multiplicative comparison says that a number is a given number of times as many as another: 20 is 4 times as many as 5.
| Topic | Remember |
|---|---|
| Multiplying | rows for ones and tens, add them |
| Dividing | divide, multiply, subtract, bring down |
| Factors, multiples | GCF is shared and greatest; LCM is shared and lowest |
| Order | ( ) then × ÷ then + − |
| Row | Work | Result |
|---|---|---|
| 1 | 58 × 6 | 348 |
| 2 | 58 × 30 | 1,740 |
| Sum | 348 + 1,740 | 2,088 |
Dice duel. Roll a die four times to make a 3-digit number and a 1-digit number. Multiply and then divide the product by the 1-digit number to get back the 3-digit number.