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P varies jointly as m and u, and varies inversely as q. Give...

P varies jointly as m and u, and varies inversely as q. Given that p = 4, m = 3 and u = 2 and q = 1, find the value of p when m = 6, u = 4 and q =\(\frac{8}{5}\)

A.

12\(\frac{8}{5}\)

B.

15

C.

10

D.

28\(\frac{8}{5}\)

Correct answer is C

P \(\propto\) mu, p \(\propto \frac{1}{q}\)

p = muk ................ (1)

p = \(\frac{1}{q}k\).... (2)

Combining (1) and (2), we get

P = \(\frac{mu}{q}k\)

4 = \(\frac{m \times u}{1}k\)

giving k = \(\frac{4}{6} = \frac{2}{3}\)

So, P = \(\frac{mu}{q} \times \frac{2}{3} = \frac{2mu}{3q}\)

Hence, P = \(\frac{2 \times 6 \times 4}{3 \times \frac{8}{5}}\)

P = \(\frac{2 \times 6 \times 4 \times 5}{3 \times 8}\)

p = 10