There are 4 quarts in a gallon. A gallon of motor oil sells for $12

4 quarts make a gallon.

1 gallon of motor oil costs $12, which means 4 quarts (in the gallon) cost $12. This implies, if bought in a gallon quantity, one quart of oil will cost $3. Therefore, to minimise the cost, the customer must maximise the quantity in gallons she buys and reduce the quantity in quarts.

6 machines with each machine consuming 5 quarts totally consume 30 quarts of oil.

To minimise the cost, the maximum quantity she could buy in gallons is 28 (largest integer less than 30 that is divisible by 4). This leaves 2 quarts to be bought individually.

Therefore, minimum cost = $(7*12) + $(2*5) = $94.

Thus, B.

total oil required = 6(machines)*5(q/machine) = 30 q
since 1 gallon = 4 quarts
30 quarts = 7g+2q
7g*$12/g+2q*$5/q = 94 $

ans- $94 (b)

Approach I - Remainder
I treated this as a remainder question.

She needs 30 quarts of oil:
6 machines * 5 quarts ea = 30 quarts

1 gallon = 4 quarts

Divide 30 by 4.

Because there are 4 quarts in one gallon, the division will yield the number of gallons plus leftover quarts --

That is, the remainder will be quarts that don't "fit" and have to be bought separately.

\(\frac{30}{4}\) = 7 + R2 (quarts)
(7 gallons * $12 per gallon) = $84
(2 quarts * $5 per quart) = $10

$84 +10 = $94 is the minimum

Answer B

Approach II - Conversion, units will cancel

M = machines
Q = quarts
G = gallons

\((6M *\frac{5Q}{1M}*\frac{1G}{4Q})= \frac{30G}{4}= 7\frac{2}{4}G\)

7 gallons plus
\(\frac{2}{4}\) of a gallon
1 gallon=\(\frac{4}{4}\) quarts
You need 2 of those 4 quarts.

Then multiply 7 gallons and 2 quarts by cost per each, and sum, as above.

Minimum is $94

Answer B

If there are 4 quarts in a gallon.
So, There are 4 Cups in 32 Ounces.