What is indirect proportion?

Answer 1

There's no such commonly recognised thing as 'indirect proportion'. If you mean Inverse Proportion, this is when one quantity decreases as another increases by the same factor.

As an example, the time it takes to run 100 m is inversely proportional to the speed you run at - if you double your speed, it takes you half as long.

Many maths problems run along the lines of "If it takes three men four days to build a wall, how long will it take five men to build the same wall?". This is inverse proportion. As you increase the number of men by a factor of 5/3, you decrease the time taken by a factor of 5/3, so the answer here is 2.4 days.

I hope that helps!