.
Let L be the lower price per dozen of eggs, in dollars (which is under the question).
Then the new price is (L+0.1) dollars per dozen. (Notice 0.1 = 0.1 dollars = 10 cents)
At the lower price, the buyer could buy
dozens for 6 dollars.
At the new price, it can buy only
dozens.
The condition says that this difference is 2 dozens:
-
= 2.
To solve this equation, multiply both sides by L*(L+0.1). You will get
6*(L+0.1) - 6L = 2*L*(L+0.1).
Simplify it step by step:
6L + 0.6 - 6L = 2L^2 + 0.2L,
0.6 = 2L^2 + 0.2L ====> 2L^2 + 0.2L - 0.6 = 0 ====> divide by 2 both sides ====>
L^2 + 0.1L - 0.3 = 0
=
=
.
The only positive root is L =
= 0.5.
Answer. The lower price was $0.5 per dozen of eggs.
Check.
= 12;
=
= 10; 12 - 10 = 2 ! Correct !
Solved.