A designer uses marbles of four different colours for his designs. The cost of each marble is the same, irrespective of the colour. The table below shows the percentage of marbles of each colour used in the current design. The cost of each marble increased by $25 \%$. Therefore, the designer decided to reduce equal numbers of marbles of each colour to keep the total cost unchanged. What is the percentage of blue marbles in the new design?

$$\begin{array}{|c|c|c|c|}\hline \textbf{Blue} & \textbf{Black} & \textbf{Red} & \textbf{Yellow}\\\hline \text{40%} & \text{25%}& \text{20%} & \text{15%}\\\hline \end{array}$$

1. $35.75$
2. $40.25$
3. $43.75$
4. $46.25$

edited

Assuming total marbles = 100

& Cost of each marble = 1 rs.

∴ To buy 100 marbles designer need to spend 100*1 = 100 rs.

After increasing price cost of 100 marbles = 125 rs.

Now, at 100 rs. the designer can buy $\dfrac{100}{125}*100$ = 80 marbles

the designer decided to reduce equal numbers of marbles of each colour to keep the total cost unchanged.

∴ (40 - x) + (25 - x) + (20 - x) + (15 - x) = 80

4x = 100 - 80

x = 5

Percentage of blue marbles in the new design = $\dfrac{40 - 5}{80}*100$

= $\dfrac{35}{80}*100$

= 43.75

Hence, the answer is option C)

by (720 points)