A person paid an interest of Rs 11,400 after 9 years on simple interest: 6% for the first 2 years, 9% for the next 3 years, and 14% for the next 4 years. How much principal did he borrow?

The principal borrowed was Rs 12,000.

Total interest rate = 6 x 2 + 9 x 3 + 14 x 4 percent.

= 12 + 27 + 56 = 95% of the principal.

So P x 95 / 100 = 11400.

P = 11400 x 100 / 95 = 12000.

In simple interest, add rate x time for each slab.