It is currently 24 Sep 2020, 19:07

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Pens cost 70 cents each and pencils cost 40 cents each. If I

Author Message
TAGS:
Retired Moderator
Joined: 07 Jun 2014
Posts: 4803
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 171

Kudos [?]: 2917 [0], given: 394

Pens cost 70 cents each and pencils cost 40 cents each. If I [#permalink]  14 Jun 2018, 14:05
Expert's post
00:00

Question Stats:

94% (01:38) correct 5% (06:06) wrong based on 18 sessions
Pens cost 70 cents each and pencils cost 40 cents each. If Iris spent $5.20 on a total of 10 pens and pencils, how many pencils did she purchase? ($1 = 100 cents)

(A) 4
(B) 6
(C) 8
(D) 10
(E) 13
[Reveal] Spoiler: OA

_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test

Retired Moderator
Joined: 07 Jun 2014
Posts: 4803
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 171

Kudos [?]: 2917 [0], given: 394

Re: Pens cost 70 cents each and pencils cost 40 cents each. If I [#permalink]  05 Jul 2018, 01:32
Expert's post
Explanation

Assign one variable to the pencils and another variable to the pens:

Number of pencils = x

Number of pens = y

$$x + y = 10$$

$$70y + 40x = 520$$

The question asks for the number of pencils, x, so isolate y in the first equation and substitute into the second:

$$y = 10 - x$$

$$70(10 - x) + 40x = 520$$

$$700 - 70x + 40x = 520$$

$$700 - 30x = 520$$

$$180 = 30x$$

$$x = 6$$

Alternatively, test the answer choices. Starting with the middle choice, if Iris bought 8 pencils and therefore 2 pens, she spent (8 × 40) + (2 × 70) = 320 + 140 = 460. That’s 60 cents too little, so Iris must have bought fewer pencils and more pens. Try 6 pencils and 4 pens: (6 × 40) + (4 × 70) = 240 + 280 = 520. (You might also have noticed that every time Iris swaps a pencil for a pen, she spends an extra 30 cents.)

Hence option B is correct!
_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test

Re: Pens cost 70 cents each and pencils cost 40 cents each. If I   [#permalink] 05 Jul 2018, 01:32
Display posts from previous: Sort by