# Help with this GCSE maths question?

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1. Use the information 639 × 8.5 = 5431.5 to find the value of
(a) 6.39×85
(b) 543.15÷850

From a non calculator paper
2. 6.39 = 639 ÷ 100
85 = 8.5 x 10
so 6.39 x 85 = 639 ÷ 100 x 8.5 x 10
= 639 x 8.5 x (10 ÷ 100)
= 5431.5 ÷ 10
= 543.15

Try using this to solve b)

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Updated: October 7, 2016
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