A, B and C enter into a partnership in the ratio $ \dfrac{7}{2} $ : $ \dfrac{4}{3} $ :$ \dfrac{6}{5} $ . After 4 months, A increases his share 50%. If the total profit at the end of one year be Rs. 21,600, then Bs share in the profit is:

Rs. 2100

Rs. 2400

Rs. 3600

Rs. 4000

Explanation:

Ratio of initial investments =$ \left(\dfrac{7}{2} :\dfrac{4}{3} :\dfrac{6}{5} \right) $= 105 : 40 : 36.

Let the initial investments be 105$ x $, 40$ x $ and 36$ x $.

$\therefore$ A : B : C =$ \left(105x \times 4 +\dfrac{150}{100} \times 105x \times 8\right) $: $\left(40 x \times 12\right)$ :$ \left(36 x \times 12\right)$

= 1680$ x $ : 480$ x $ : 432$ x $ = 35 : 10 : 9.

Hence, Bs share = Rs.$ \left(21600 \times\dfrac{10}{54} \right) $= Rs. 4000.