Video: KS2-M17 • Paper 1 • Question 35

1 1/2 × 57 = _.

03:14

Video Transcript

One and a half multiplied by 57 equals what?

The question is asking us to multiply a mixed number, one and a half, by an integer, 57. The easiest way to do this is to make both of the numbers into fractions. One and a half is equal to three-halves. So we need to multiply three-halves by 57. We would write 57 as 57 over one.

Now, we can multiply three over two or three-halves by 57 over one. Let’s start by multiplying the numerators, three multiplied by 57. Three times 50 is 150. Three times seven is 21. 150 plus 21 makes 171. Next, we need to multiply the denominators: two times one is two.

171 halves is an improper fraction. The numerator is larger than the denominator. We need to write our answer as a mixed number. In other words, how many whole numbers can we make out of 171 halves and are there any halves left over. We need to divide 171 by two.

100 divided by two or halved is 50, 70 divided by two is 35, and one divided by two gives us 0.5 or a half. We can add together the 50 and the 35 to give us 85. And we have a half left over. 171 halves is equal to 85 and a half. We could also write this as 85.5. Either of these answers is acceptable.

To find one and a half multiplied by 57, first we wrote both these numbers as fractions: three-halves multiplied by 57 over one. Then, we multiplied the numerators: three times 57 gave us 171. Next, we multiplied the denominators: two times one equals two.

171 halves or 171 over two is an improper fraction. We divided 171 by two, which tells us that 171 halves is equal to 85 and a half.

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