Soldier march calculation

The soldiers walked 90km in 3 days. The next day, they left twice more than the first day and the third day three times more than the second day. How many km did they march on each day?

Final Answer:

a =  10
b =  20
c =  60

Step-by-step explanation:


a+b+c=90
b = 2a
c = 3b

a+b+c=90
b = 2·a
c = 3·b

a+b+c = 90
2a-b = 0
3b-c = 0

Pivot: Row 1 ↔ Row 2
2a-b = 0
a+b+c = 90
3b-c = 0

Row 2 - 1/2 · Row 1 → Row 2
2a-b = 0
1.5b+c = 90
3b-c = 0

Pivot: Row 2 ↔ Row 3
2a-b = 0
3b-c = 0
1.5b+c = 90

Row 3 - 1.5/3 · Row 2 → Row 3
2a-b = 0
3b-c = 0
1.5c = 90


c = 90/1.5 = 60
b = 0+c/3 = 0+60/3 = 20
a = 0+b/2 = 0+20/2 = 10

a = 10
b = 20
c = 60

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