sohaib_iba wrote:Ellen paid $11.80 for 40 postage stamps. If some of the stamps were 33-cent stamps and the rest were 23-cent stamps, how many 33-cent stamps did she buy?
A) 13
B) 17
C) 22
D) 25
E) 26
Please help me at this question as i am unable to solve it yet. Thanks in advance
I get 26.
The question stem screams EQUATIONS. And this stem gives you two. First set up your variables
X = quantity of 33 cent postage stamps (your answer)
Y = quantity of 23 cent postage stamps
(1) X+Y = 40 (since you have 40 total stamps)
(2) .33*X + .23*Y = 11.80 (since you paid 11.80 for all the stamps)
Take (2) and multiply through by 100 to clear out the decimals
33*X + 23*Y = 1180
Take (1) and multiply through by -23
-23*X - 23*Y = 40*-23
Add these two together. Skipping the arithmetic involved in canceling the Y's:
10*X = 1180 - 40*23
X = 118 - 4*23
X = 26
