A mathematics teacher posed the following problems to her students :
A. Simrat pays ₹ 60,000 as rent for three months. How much will she have to pay for a whole year if the rent per month remains same ?
B. Cost of three dozen bananas is ₹ 45. Calculate the number of bananas that can be purchased for ₹ 12.50.
C. Joey and Jenny are going to school. Joey started walking before Jenny. When Joey was at the third block, Jenny was at the first block. If both are walking with the same speed, then where would Jenny be if Joey is at the ninth block ?
Which of the following is correct with respect to the above three questions ?

The correct option is A and B are daily life problems based on unitary method.

Let us analyze each of the three given problems to understand which ones are based on the unitary method:

Problem A:
"Simrat pays ₹ 60,000 as rent for three months. How much will she have to pay for a whole year if the rent per month remains same ?"
In this problem, we first find the rent for 1 month (single unit) by dividing ₹ 60,000 by 3 months:

Rent per month = ₹ 60,000 / 3 = ₹ 20,000

Then, we find the rent for a full year (12 months) by multiplying the single unit value by 12:

Rent for a year = ₹ 20,000 × 12 = ₹ 2,40,000

Since this involves finding the value of a single unit first to determine the required total, Problem A is a daily life problem based on the unitary method.

Problem B:
"Cost of three dozen bananas is ₹ 45. Calculate the number of bananas that can be purchased for ₹ 12.50."
Here, 3 dozen bananas equal 36 bananas. We find the cost of 1 banana (single unit) or how many bananas per rupee:

Cost of 1 banana = ₹ 45 / 36 = ₹ 1.25

Then, we calculate how many bananas can be bought for ₹ 12.50:

Number of bananas = 12.50 / 1.25 = 10

Since this also relies on calculating a single unit rate to solve the main question, Problem B is a daily life problem based on the unitary method.

Problem C:
"Joey and Jenny are going to school. Joey started walking before Jenny. When Joey was at the third block, Jenny was at the first block. If both are walking with the same speed, then where would Jenny be if Joey is at the ninth block ?"
In this problem, the difference in position between Joey and Jenny is constant because they are walking at the same speed. Joey is 2 blocks ahead of Jenny (3 - 1 = 2). When Joey is at the 9th block, Jenny will be at block (9 - 2 = 7). This problem involves additive difference/constant offset, NOT direct proportion or unitary rates. Therefore, Problem C is not based on the unitary method.

Thus, only questions A and B are daily life problems based on the unitary method.