Question

if 4/9 of a gas tank can be filled in two minutes then how many minutes will it take to fill the whole gas tank

Answer 1

`\frac { 4 }{ 9 } =2M\\ \\ \frac { 1 }{ 2 } \cdot \frac { 4 }{ 9 } =\frac { 1 }{ 2 } \cdot 2M\\ \\ \frac { 4 }{ 18 } =M\\ \\ \therefore \quad M=\frac { 2 }{ 9 }`

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Every minute 2/9 of the tank is filled up. That means that every half minute 1/9 of the tank is filled up.

2/9 + 2/9 + 2/9 + 2/9 + 1/9 = 9/9

Therefore:

M + M + M + M + 1/2M = 9/9

(4+1/2)M=9/9

So it would take 4 and a half minutes to fill the whole gas tank.