Part 6 of 17 · 2 minCompound Interest

The chapter was compound interest and Chinnu had been stuck on the same sum for forty minutes.

She was not bad at maths. She was ten and it was a horrible sum: a principal of eight thousand, a rate she kept mis-copying, three years, compounded annually, and the answer at the back of the book refused to be the answer she got.

Bujji had given up long ago and was drawing on the last page.

Ammamma sat down on the floor beside them — properly on the floor, at seventy-eight, in one movement — and said, "Read it out."

Chinnu read it out.

Ammamma looked at the ceiling for a moment.

Then she said a number.

Chinnu checked the back of the book, mostly to be kind about it.

It was the number.

"How did you—" She stopped. "Ammamma, how did you do that?"

"You add the interest to the money, and then you do it again," said Ammamma, as though explaining which bus to take. "Three times. That is all it is. They put a formula on it so that it looks like a big thing."

"Do another one. Do a different one."

She did four more. She got all four. On the fifth she made a small mistake in the second year and caught it herself, halfway through, and went back and fixed it, and said "chi" at her own carelessness.

She could not have told you what day it was. She had asked Chinnu twice that afternoon whether Nanna had come home. But she took eight thousand rupees at nine per cent through three years in her head like a woman going down a familiar staircase in the dark.

Amma was standing in the doorway with a plate in her hand.

"She ran the tiffin business for twenty-two years," she said. "Forty households. Different rates for the ones who paid monthly and the ones who paid weekly. Credit for the ones having a bad year. She never wrote any of it in a book — because if you write it in a book, people can see what you have forgiven them, and she did not want them to see."

Chinnu sat there with her pencil.

She had spent a month collecting the funny things her grandmother did.

It had not once occurred to her to find out what her grandmother could do.