Correct Answer: He will invest 4.000 Tk. in company ‘M’ and (9,000 – 4.000) = 5.000 Tk. in company ‘N

Explanation:

Let. He invested Tk. x in company ‘M’ at 10%

In ‘N’ Company, he invested tk. (9.000 -x) at 9%

We kaow, I = $\frac{P\times r\times n}{100}$

The amount of interest at 10% of Tk. x =$\frac{x\times 10\times 1}{10}$=$\frac{x}{10}$ tk

And the amount of interest at 9% of Tk. (9.000 -x)=$\frac{9(9000-x)}{100}$

According to question. $\frac{x}{10}$+$\frac{9(9000-x)}{100}$= 850

=> $\frac{10x+81000-9x}{100}$ = 850

=> x+81,000 = 85,000

=> x = 85,000-81,000

so, x = 4,000

He will invest 4.000 Tk. in company ‘M’ and (9,000 – 4.000) = 5.000 Tk. in company ‘N