The business

The business earned CZK 98,400 in the shop in three weeks. In the second week, sales were 20% higher than the first week. The third week was 10% lower than the second week. How much did the business earn each week?

Correct answer:

a =  30000
b =  36000
c =  32400

Step-by-step explanation:


a+b+c=98400
b = a + 20/100 a
c = b - 10/100 b

a+b+c=98400
b = a + 20/100·a
c = b - 10/100·b

a+b+c = 98400
120a-100b = 0
90b-100c = 0

Pivot: Row 1 ↔ Row 2
120a-100b = 0
a+b+c = 98400
90b-100c = 0

Row 2 - 1/120 · Row 1 → Row 2
120a-100b = 0
1.833b+c = 98400
90b-100c = 0

Pivot: Row 2 ↔ Row 3
120a-100b = 0
90b-100c = 0
1.833b+c = 98400

Row 3 - 1.83333333/90 · Row 2 → Row 3
120a-100b = 0
90b-100c = 0
3.037c = 98400


c = 98400/3.03703704 = 32400
b = 0+100c/90 = 0+100 · 32400/90 = 36000
a = 0+100b/120 = 0+100 · 36000/120 = 30000

a = 30000
b = 36000
c = 32400

Our linear equations calculator calculates it.



Did you find an error or inaccuracy? Feel free to write us. Thank you!







Tips for related online calculators
Our percentage calculator will help you quickly calculate various typical tasks with percentages.
Do you have a system of equations and looking for calculator system of linear equations?

You need to know the following knowledge to solve this word math problem:

Units of physical quantities:

Grade of the word problem:

Related math problems and questions: