Question

suppose a varies directly as b, and a=7 when b=2 find b when a =21

Answer 1

because α varies directley to β
$\alpha = k \beta$
(k = constant)

α=7 when β=2
7= 2k
k= $\frac{7}{2}$

so when α=21
21= $\frac{7}{2}$ b
b= 6