Below is an instruction that describes a task. Write a response that appropriately completes the request in Swahili. Please answer in Swahili.

### Instruction:
Betty is 60 years old, and she is the oldest person in the family. Her daughter is 40 percent younger than she is, and her granddaughter is one-third her mother's age. How old is the granddaughter?

### Response:
 Tofauti ya umri kati ya Betty na binti yake ni miaka 60 * 40/100 = <<60*40/100=24>>24.
Ikiwa binti ni mdogo kwa miaka 40 kuliko Betty, basi yeye ana umri wa 60 - 24 = <<60-24=36>>36.
Mjukuu ana umri wa 1/3 * 36 = <<1/3*36=12>>12.