Puzzle challenge: Can you do this calculation to help your grandmother?

New Delhi: Problem-solving in mathematics supports the development of the ability to think creatively, critically and logically. This also helps human being to use their mathematical knowledge to solve hypothetical and real-world problems. If you know all the benefits and enjoy all the intellectual challenges then we can assure you that you are going to love the below-mentioned mathematical puzzle.

The puzzle is divided into five stages that start with the puzzle, the condition, the question, the answer and how we cracked the riddle:

Situation:

A grandmother, who lives in Kashmir, has 30 grandchildren. As she loves them very much, she decides to knit one woolly hat for each of her thirty grandchildren. She also set the deadline to have them all ready on Christmas Eve. She is sure that she can knit all the hats at a time but there is a condition, available below.

Condition:

The condition is that the grandmother can only knit two hats a week (starting from the day she decides to knit them). She knits every day without failing and paying attention to the calendar. After a few weeks, she realized that it takes her one whole week to knit each hat.

Before the deadline, she managed to knit enough for half her grandchildren.

Question: On what day does she have this realisation?

Answer: The grandmother has this realisation on Christmas Eve.

How we cracked the puzzle

The situation states that the grandmother has to make 30 hats, knitting two caps in one week. With this speed, she will take 15 weeks to make 30 hats. But, she failed to prepare two hats in one week. If she has knitted enough for only half of her grandchildren, it means only 15 hats are ready on the deadline. In one week, she makes one. So, she must have taken 15 weeks to prepare 15 hats.

She must have realised it the Christmas Eve.