Bela has ₹100 for pocket money. She spends 5 every day. What amount will be left on the 15th day? How many days will it take for the entire amount to be spent?

Let n be the number of days and A be the amount left (in ₹) after n days.

Since Bela starts with ₹100 and spends ₹5 every day, the amount left after n days is:

A = 100 − 5n

Amount left on the 15th day:

Substituting n = 15 in A = 100 − 5n:

A = 100 − 5 × 15

⇒ A = 100 − 75

⇒ A = 25

So, ₹25 will be left on the 15th day.

Number of days for the entire amount to be spent:

The entire amount is spent when A = 0.

Substituting A = 0 in A = 100 − 5n:

100 − 5n = 0

⇒ 5n = 100

⇒ n = $\dfrac{100}{5}$

⇒ n = 20

So, it will take 20 days to spend the entire amount.

Hence, ₹25 will be left on the 15th day, and it will take 20 days for the entire amount to be spent.