SOLUTION: Solve this word problem. The cost of 1000 cubic feed of natural gas is $39 and the cost of 3000 cubic feet is $99. There is a linear equation that expresses the cost C in terms o

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Question 63791: Solve this word problem. The cost of 1000 cubic feed of natural gas is $39 and the cost of 3000 cubic feet is $99. There is a linear equation that expresses the cost C in terms of the number of cubic feet n. Find the equation and find the cost of 2400 cubic feet of natural gas.
Please explain the procedure you used to solve this problem.
Thank you.
Answer by venugopalramana(3286) About Me  (Show Source):
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Solve this word problem. The cost of 1000 cubic feed of natural gas is $39 and the cost of 3000 cubic feet is $99. There is a linear equation that expresses the cost C in terms of the number of cubic feet n. Find the equation and find the cost of 2400 cubic feet of natural gas.
Please explain the procedure you used to solve this problem.
Thank you.
LET COST OF GAS C BE RELATED TO QUANTITY Q BY THE LINEAR RELATION
C=A*Q+B.WHERE A AND B ARE CONSTANTS TO BE FOUND.
WEW HAVE C=39$ WHEN Q=1000 CUF AND C=99$ WHEN Q = 3000 CUF.SO
1000A+B=39................1
3000A+B=99...................2
EQN.2 - EQN.1
3000A+B-1000A-B=99-39
2000A=60
A=60/2000=3/100=0.03
PUTTING IN EQN.1
1000*0.03+B=39
30+B=39
B=39-30=9
HENCE
C=0.03Q+9 IS THE LINEAR RELATION