Whole Numbers
Topics
- Multiplying by 5 and 25Free
- Multiplying by 9 and 99Pro
- Multiplying by 11 and 101Pro
- Multiplying by 125 and 250Pro
- Squaring numbers ending in 5Pro
- How the Product Depends on Its FactorsPro
- How the Quotient Depends on the Dividend and DivisorPro
- Addition and Subtraction. Adding and Subtracting a Sum and a DifferencePro
- How the Numbers and the Result Are Linked in Multiplication and DivisionPro
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Multiplying by 5 and 25
- To ×5, multiply by 10 and halve; ×25 is ×100 then ÷4; ×50 is ×100 then ÷2.
- 36·5 in one move: ×10, then halve. What do you get? ×5 = ×10 ÷ 2: 36·10=360, halved = 180.
- 64·25 is 64·100÷4. How much? ×25 = ×100 ÷ 4: 6400÷4 = 1600.
- 84·50 in one move: ×100 ÷ 2. What do you get? ×50 = ×100 ÷ 2: 8400÷2 = 4200.
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