Earned 30451

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

Correct answer:

a =  30000
b =  36000
c =  32400

Step-by-step explanation:


a+b+c=98400
b = a+0.20·a
c = b - 0.10 · b

a+b+c = 98400
1.2a-b = 0
0.9b-c = 0

Pivot: Row 1 ↔ Row 2
1.2a-b = 0
a+b+c = 98400
0.9b-c = 0

Row 2 - 1/1.2 · Row 1 → Row 2
1.2a-b = 0
1.833b+c = 98400
0.9b-c = 0

Row 3 - 0.9/1.83333333 · Row 2 → Row 3
1.2a-b = 0
1.833b+c = 98400
-1.491c = -48305.455


c = -48305.45454545/-1.49090909 = 32400
b = 98400-c/1.83333333 = 98400-32400/1.83333333 = 36000
a = 0+b/1.2 = 0+36000/1.2 = 30000

a = 30000
b = 36000
c = 32400

Our linear equations calculator calculates it.



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