Correct Answer: Additional Tk. 56,000 is needed to make income equal.

Explanation:

Let, he has to invest more Tk. x at 10% interest

Then his total investment will be = (24,000 + x) Tk.

Now at 7.5%, the amount of interest on Tk. 24,000 = (24000$\times \frac{7.5}{100}$) TK

At 10%, the amount of interest on Tk. x =(x$\times \frac{10}{100}$) TK

At 9.25%, the amount of interest on Tk. (24,000 + x) = (24,000 + x)$\times \frac{9.25}{100}$)

=> $\frac{180000}{100}$+$\frac{10x}{100}$ = $\frac{222000+9.25x}{100}$

=> 1,80,000 + 10x = 2,22,000 + 9.25

=> 10x – 9.25x = 2,22,000 -1,80,000

=> 0.75x = 42,000

=> x = $\frac{42000}{0.75}$

x = 56,000