Multiplying and dividing fractions · Usually met around P5
Multiplying fractions
Tops times tops, bottoms times bottoms.
How to do it
Method
Tops times tops, bottoms times bottoms
23 × 34 = 612 = 12
One more example
2 × 38 = 68 = 34
In full
A fraction times a fraction: multiply the tops, multiply the bottoms, then simplify: 23 × 34 = 612 = 12. Or cancel first to keep the numbers small. In 23 × 34, the 3 on top and the 3 below cancel, and the 2 on top and the 4 below can both ÷ 2, leaving 12. A fraction times a whole number: multiply the top by the whole number, and keep the bottom the same: 2 × 38 = 68 = 34. 12 × 34 is 34 of 12: 12 ÷ 4 = 3, 3 × 3 = 9. Cancel before or simplify after. Either way, the answer comes out the same.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
8 × 12
Show the answer and working
Answer: 8 × 12 = 4
8 × 12: that's 12 of 8, 8 ÷ 2 = 4, 4 × 1 = 4
Example 2
14 × 3
Answer in simplest form
Show the answer and working
Answer: 14 × 3 = 34
14 × 3: the whole number times the top, 3 × 1 = 3, the bottom unchanged → 34, already in simplest form
Example 3
13 × 2
Answer in simplest form
Show the answer and working
Answer: 13 × 2 = 23
13 × 2: the whole number times the top, 2 × 1 = 2, the bottom unchanged → 23, already in simplest form
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