Question 1142129: 3 litre of oil and 30 litre of petrol cost R45 while 7 litre and 15 litre of petrol cost R40.Calculate the price of the oil. Found 2 solutions by ankor@dixie-net.com, josgarithmetic:Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website! let a = the price of oil
let b = the price of petrol
:
write an equation for each statement
:
3 litre of oil and 30 litre of petrol cost R45
3a + 30b = 45
:
while 7 litre and 15 litre of petrol cost R40.
7a + 15b = 40
:
Calculate the price of the oil.
Use elimination, multiply the 2nd equation by 2, subtract the 1st equation
14a + 30b = 80
3a + 30b = 45
---------------subtraction eliminates b, find a
11a + 0 = 35
a = 35/11
a = $3.18 for oil
:
Use the 1st equation to find b,
3(3.18) + 30b = 45
9.54 + 30b = 45
30b = 45 - 9.54
30b = 35.46
b = 35.46/30
b = $1.18 for petrol
:
:
See if these awkward solutions check out in the 2nd equation
7(3.18) + 15(1.18) =
22.26 + 17.70 = 39.96 ~ 40
(