# A is directly proposional to the square of b. If a=16 when b=2, find the value of a when b=5?

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### Sandeep Dalton

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When A is directly proportional to Bsquared, there is also another constant factor involved. We call this constant factor k. Firstly we need to work out the relationship between A in B as an equation. Here it is: A = K x Bsquared. Secondly we need to work out what K is. When A is 16, Bsquared is 4 (2ร2). In other words 16 = k x 4. So K is 16/4 which is 4. Lastly lets work out A when B is 5. A = K x Bsquared. We know k is 4 and BSquares is 25 (5x5) so A = 4 x 25 A = 100 Hope that helped! Sandy

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