In a school, if the ratio of the number of pupils to teachers is 20:1 and the number of pupils is 840, how many teachers are there?

• A. 42
• B. 40
• C. 38
• D. 44

Answer: (A)

To determine the number of teachers in the school, you can start by understanding the given ratio of pupils to teachers, which is 20:1. This means that for every 20 pupils, there is 1 teacher.

Given that there are 840 pupils, you can set up a proportion based on the ratio. Since the ratio indicates that 20 pupils correspond to 1 teacher, you can calculate the number of teachers by dividing the total number of pupils by the number of pupils per teacher:

Number of teachers = Total number of pupils ÷ Number of pupils per teacher

Here, that would be:

Number of teachers = 840 ÷ 20

Carrying out the division:

Number of teachers = 42

This calculation shows that there are 42 teachers in the school. This demonstrates how the ratio can be directly applied to determine the required number of teachers based on the known quantity of pupils.