Potatoes

For three days, the store sold 1400 kg of potatoes. On the first day, they sold 100 kilograms of potatoes less than on the second day. On the third day, three-fifths of what they sold the first day. How many kgs of potatoes are sold every day?

Correct answer:

a =  500
b =  600
c =  300

Step-by-step explanation:


a+b+c=1400
a = b-100
c = 3/5·a

a+b+c = 1400
a-b = -100
3a-5c = 0

Pivot: Row 1 ↔ Row 3
3a-5c = 0
a-b = -100
a+b+c = 1400

Row 2 - 1/3 · Row 1 → Row 2
3a-5c = 0
-b+1.667c = -100
a+b+c = 1400

Row 3 - 1/3 · Row 1 → Row 3
3a-5c = 0
-b+1.667c = -100
b+2.667c = 1400

Row 3 + Row 2 → Row 3
3a-5c = 0
-b+1.667c = -100
4.333c = 1300


c = 1300/4.33333333 = 300
b = -100-1.6666666666667c/-1 = -100-1.66666667 · 300/-1 = 600
a = 0+5c/3 = 0+5 · 300/3 = 500

a = 500
b = 600
c = 300

Our linear equations calculator calculates it.



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