Question

If D varies directly with t and D is 105 when t is 3, find D when t is 8.

35
280
840

Answer 1

280

Explanation:

D = kt

105 = k(3)

k = 35

D = 35t

D = 35(8) = 280

Answer 2

280

Explanation:

Let the variation component be "k"

D = kt

When D = 105 and t = 3,

105 = 3k

Divide both sides by 3 to get the value of "k"

105/3 = 3k/3

k = 35

When t = 8,

D = kt

D = 35 x 8

D = 280