Mathematics
Grade10
Easy
Question
The ratio of incomes of two persons is 9:7, and the ratio of their expenditure is 4:3. If each of them manages to save $2000 per month, find their monthly expenditure?
- $16000, $12000
- $8000, $10000
- $11000, $20000
- None of the above
Hint:
An equation with the maximum order of 1 and an equation of a straight line is called the linear equation.
The correct answer is: $16000, $12000
Step 1 of 1:
We have given the ratio of incomes of two persons is 9:7, and the ratio of their expenditure is 4:3. If each of them manages to save $2000 per month
Let the income be x and expenditure be y
Saving per month = $2000
Then
9x – 4y = 2000………………….. 1
7x – 3y = 2000……………… 2
From 1
9x – 4y = 2000
9x = 2000 + 4y
x = 
Substituting x in 2nd equation,
7 
- 3y = 2000
- 3y = 2000
14000+ 28y – 27y = 18000
14000 + 1y = 18000
y = 4000
4y = 4 x 4000
=16000
3y = 3 x 4000
= 12000
The substitution method is the algebraic method to solve simultaneous linear equations.
