26,271 views
20 votes
20 votes
If motor oil sells at 3 quarts for $2.83 what will 5 quarts cost

User Amaurea
by
2.9k points

1 Answer

19 votes
19 votes

Answer: The correct answer is:

___________________

" 5 [five] quarts of motor oil will cost:

→ " $ 4.72 " .

___________________

First method of solving the problem:

Set up a ratio/proportion; in the form of an equation—using fractions— as follows:

___________________


(3qt)/(2.83) = (5 qt)/(x) ; → in which we are to solve for "x" {value in "dollars".}.

___________________

Now, let's "cross-factor multiply" the values in the equation:

3*(x) = (2.83) * 5 ;

___________________

Now, simplify—and rewrite the equation:

___________________

3x = 14.15 ;

___________________

Now, divide Each side of the equation by "3" ;

to isolation "x" on one side of the equation;

& to solve for "x" ;

___________________

3x / 3 = (14.15) / 3 ;

to get: x = 4.71666666.... (dollars);

___________________

Let us round that number up to: "4.72" ;

{since: "4.71" ; is followed by a digit higher than "4" } ;

___________________

The correct answer is:

→ " 5 [five] quarts of motor oil will cost: " $ 4.72 " .

___________________

Second method of solving this problem:

1) First: We treat this problem as a "unit rate" problem;

{that is; given a numeric quantity per certain numeric value;

→ we reduce/solve for what that Particular Quantity is,

per that particular [Single] Unit numeric value.

→ For this particular problem; we are given:

$ 2.83 ["2.83 dollars"] ; per " 3 quarts " ;

We began by reducing/solving this cost (in dollars);

→ "per quart" ; [i.e. per "one quart"] ;

[i.e. per "single, unit quart"] ;

So; "
(2.83 dollars)/(3quarts) = ((2.83)/(3)) (dollars)/(quart) " ;

= (2.83 ÷ 3) dollars/quart ;

= 0.94333333333............. dollars per quart.

___________________

2) Second: Then: We take that value; and to find the cost of "5 (five) quarts" (as the problem asks)—we multiply that value by "5" :

→ Using calculator:

→ 0.943333333333333333333333.... * 5 ;

= 4.7166666666.. dollars ;

→ which is the same answer obtained from the first method.

___________________

Third method of solving the problem:

This is really just an extension of the second method directed aforementioned:

___________________


(2.83 dollars)/(3quarts) * (5 quarts)/(1) = ? ;

→ The units of "quarts" cancel out; since: [" quarts/quarts = 1 "] ;

___________________

and we have:


((2.83) *5)/(3) dollars ;

→ (2.83) * 5 = 14.15 ;


((2.83) *5)/(3) = ((14.15))/(3) ;

= (14.15) ÷ 3 ; = 4.716666666666 ...

→ which is the same answer from the other 2 (two) aforementioned methods.

→ Let us round that number up to: "4.72" ;

{since: "4.71" ; is followed by a digit higher than "4" } ;

___________________

So: The correct answer is:

___________________

" 5 [five] quarts of motor oil will cost: $ 4.72 . "

___________________

Hope this is helpful to you! Best of luck to you!

User Starkers
by
3.1k points
Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.