Question

In a row of 40 children, R is 11th from the right and there are 15 children between R and M. What is M's position from the left end of the row? 

• A. 14th
• B. 15th
• C. 13th
• D. Can't be determined
• E.

Hint:

Always check whether the positions given in the problem make sense based on the total number of elements in the set.

Answer 1

The Correct Option is A

- Total number of children = 40. - R is 11th from the right, so R's position from the left is: \[ 40 - 11 + 1 = 30. \] - There are 15 children between R and M, so M is at the 30th + 15 + 1 = 46th position. However, since there are only 40 children, the solution cannot be determined in this case. Thus, the correct answer is (a) 14th.

Answer 2

Since adding 15 in one direction would push past the end of a 40-person row, work out the only feasible side M can be on, then compute directly.

1. R's position counted from the left end is \( 40 - 11 + 1 = 30 \).
2. If M were placed 15 positions to the right of R, M would sit at \( 30 + 15 + 1 = 46 \), which is beyond the 40 people in the row, so this is impossible.
3. So M must sit on the left side of R instead, with 15 children in between: M's position from the left is \( 30 - 15 - 1 = 14 \).

Checking the other options, 15th and 13th do not correctly account for the 15 children strictly between R and M, and "Can't be determined" is ruled out because the row's length of 40 fixes M's side uniquely.

Hence, the correct answer is 14th.