Volga, a famous pastry parlour in Hamirpur, sells three varieties of pastry: Chocolate, Vanilla and Mix Fruit. Their demand in January was in the ratio $13 : 16 : 21$. In February the demand rose by 100%, 50% and $33\tfrac{1}{3}\%$ respectively. In March, demand for both Chocolate and Mix Fruit rose by 25%, while Vanilla's demand became equal to the mean of the three varieties. Find the percentage increase in Vanilla's demand from February to March.
Answer and solution
Correct answer: A
Solution
January: $13, 16, 21$. February: $26, 24, 28$.
March: Chocolate $= 32.5$, Mix Fruit $= 35$, Vanilla $= V$
$V = \dfrac{32.5 + V + 35}{3} \Rightarrow 2V = 67.5 \Rightarrow V = 33.75$
Increase $= \dfrac{33.75 - 24}{24} \times 100 = 40.625\% \approx 40.6\%$
March: Chocolate $= 32.5$, Mix Fruit $= 35$, Vanilla $= V$
$V = \dfrac{32.5 + V + 35}{3} \Rightarrow 2V = 67.5 \Rightarrow V = 33.75$
Increase $= \dfrac{33.75 - 24}{24} \times 100 = 40.625\% \approx 40.6\%$