Question

a man who spends 20% of his salary and saves Rs. 1500 per month. Find his expenses

Answer 1

1. We assume, that the number 1500 is 100% - because it's the output value of the task.
2. We assume, that x is the value we are looking for.
3. If 1500 is 100%, so we can write it down as 1500=100%.
4. We know, that x is 20% of the output value, so we can write it down as x=20%.
5. Now we have two simple equations:
1) 1500=100%
2) x=20%
where left sides of both of them have the same units, and both right sides have the same units, so we can do something like that:
1500/x=100%/20%
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for what is 20% of 1500

1500/x=100/20
(1500/x)*x=(100/20)*x - we multiply both sides of the equation by x
1500=5*x - we divide both sides of the equation by (5) to get x
1500/5=x
300=x
x=300

now we have:
20% of 1500=300