One tamk of gasoline has an octane rating of 140 and another tank of gasoline has an octane rating of 80. to obtain a mixture of 60 gallons with an octane rating of 120, how many gallons should be used from the tank with the octane rating of 80?

20 gallons were used from the tank with the octane rating of 80.

Step-by-step explanation:

Given : One tank of gasoline has an octane rating of 140 and another tank of gasoline has an octane rating of 80. To obtain a mixture of 60 gallons with an octane rating of 120.

To find : How many gallons should be used from the tank with the octane rating of 80?

Solution : Let x be the volume of gas whose octane rating is 140 and

y be the volume of gas whose octane rating is 80.

Then, we form the equation as:

(1)

or   .........[3]

(2)

Now multiply equation (2) by 4  

...........[4]

Subtract (4) from (3)  

Put x in equation [4] we get,

Therefore, x=40 and y=20

So, 20 gallons were used from the tank with the octane rating of 80.

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i think the correct option is the second option.