Problema Solution
The gas price index for 1985 was 212.9 and the gas index for 2000 was 276.9. If it cost $18.71 to fill your gas tank in 1985, how much would it have cost to fill the same tank in 2000?
Answer provided by our tutors
since index number = (value/reference number)*100 we have
for the year of 1985
212.9 = (18.71/(reference value))*100 divide both sides by 100
18.71/(reference value) = 2.129
reference value = 18.71/2.129
for the year of 2000
276.9 = (x/(reference value))*100
where x is the cost to fill your gas tank
if we plug reference value = 18.71/2.129 into 276.9 = (x/(reference value))*100 we get
(x/(18.71/2.129))*100 = 276.9
by solving we find
x = $24.33
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in the year of 2000 it would cost $24.33 to fill the gas tank.