JAMB - Mathematics (1986 - No. 16)

If x varies directly as y3 and x = 2 when y = 1, find x when y = 5
2
10
125
250

Explanation

x \(\alpha\) y3

x = ky3

k = \(\frac {x}{y^3}\)

when x = 2, y = 1

k = 2

Thus x = 2y3 - equation of variation

= 2(5)3

= 250

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