Bringing 4709

The passing freight train had a total of 42 wagons, bringing a total of 750 tons to the station.
Some wagons were 15 tons, and others 20 tons.
How many wagons were 15 tons, and how many were 20 tons?

Correct answer:

a =  18
b =  24

Step-by-step explanation:


a+b=42
750 = 15a + 20b

a+b=42
750 = 15·a + 20·b

a+b = 42
15a+20b = 750

Pivot: Row 1 ↔ Row 2
15a+20b = 750
a+b = 42

Row 2 - 1/15 · Row 1 → Row 2
15a+20b = 750
-0.33b = -8


b = -8/-0.33333333 = 24
a = 750-20b/15 = 750-20 · 24/15 = 18

a = 18
b = 24

Our linear equations calculator calculates it.



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