If 5 dollars and 35 crowns is equivalent to 7 pounds, and 4 dollars and 4 pounds is equivalent to 56 crowns, 1 pound and 28 crowns is equivalent to how many dollars?
$7.00
$7.50
$8.50
$9.00
$10.00
The OA is A.
Experts, can you help me here? What are the equations I should set here? Thanks in advanced.
If 5 dollars and 35 crowns is equivalent to 7 pounds......
This topic has expert replies
-
- Master | Next Rank: 500 Posts
- Posts: 415
- Joined: Thu Oct 15, 2009 11:52 am
- Thanked: 27 times
Or algebraically:
Let X = number of crowns/pound
Y = crowns/dollar
therefore number of dollars/pound = X/Y
Since you're trying to find the number of dollars, rearrange the two given statements to equal dollars:
5 = 7*X/Y - 35/Y
4 = 56/Y - 4*X/Y
Use the first statement to solve for Y. Multiply both sides by Y: 5*Y = 7*x -35> therefore Y=(7*X-35)/5
Multiply the second statement both sides by Y: 4*Y = 56-4*X
Substitute Y=(7*X-35)/5: 4(7*X-35)/5 = 56 - 4*X
Solve for X= 105/12 = 35/4.
Substitute this value of X to solve for Y = (7*(35/4) - 35)/5 = 21/4
The question asks for how many dollars equals 1 pound and 28 crowns. Algebraically, this equals :
1*(X/Y) + 28/Y = (35/21) + 28*(4/21)
= 7(5 + 16)/21 = 7,A
Let X = number of crowns/pound
Y = crowns/dollar
therefore number of dollars/pound = X/Y
Since you're trying to find the number of dollars, rearrange the two given statements to equal dollars:
5 = 7*X/Y - 35/Y
4 = 56/Y - 4*X/Y
Use the first statement to solve for Y. Multiply both sides by Y: 5*Y = 7*x -35> therefore Y=(7*X-35)/5
Multiply the second statement both sides by Y: 4*Y = 56-4*X
Substitute Y=(7*X-35)/5: 4(7*X-35)/5 = 56 - 4*X
Solve for X= 105/12 = 35/4.
Substitute this value of X to solve for Y = (7*(35/4) - 35)/5 = 21/4
The question asks for how many dollars equals 1 pound and 28 crowns. Algebraically, this equals :
1*(X/Y) + 28/Y = (35/21) + 28*(4/21)
= 7(5 + 16)/21 = 7,A
GMAT/MBA Expert
- Scott@TargetTestPrep
- GMAT Instructor
- Posts: 7242
- Joined: Sat Apr 25, 2015 10:56 am
- Location: Los Angeles, CA
- Thanked: 43 times
- Followed by:29 members
To solve this problem, we need to determine the equivalent of 1 pound to dollars and 1 crown to dollars. Let d = value of 1 dollar, c = value of 1 crown and p = value of 1 pound. We are given that:Vincen wrote:If 5 dollars and 35 crowns is equivalent to 7 pounds, and 4 dollars and 4 pounds is equivalent to 56 crowns, 1 pound and 28 crowns is equivalent to how many dollars?
$7.00
$7.50
$8.50
$9.00
$10.00
5d + 35c = 7p
4d + 4p = 56c
We can simplify the second equation as d + p = 14c. Let's isolate d in each equation:
5d = 7p - 35c → [1]
d = -p + 14c → [2]
If we multiply equation [2] by 7 and add that to equation [1], we have:
12d = 63c
c = 12d/63 = 4d/21
Similarly, if we multiply equation [1] by 2 and equation [2] by 5 and add those together, we have:
15d = 9p
p = 15d/9 = 5d/3
Thus, 1 pound and 28 crowns is equivalent to:
5d/3 + 28 x 4d/21 = 5d/3 + 16d/3 = 21d/3 = 7d or 7 dollars
Answer: A
Scott Woodbury-Stewart
Founder and CEO
[email protected]
See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews
- EconomistGMATTutor
- GMAT Instructor
- Posts: 555
- Joined: Wed Oct 04, 2017 4:18 pm
- Thanked: 180 times
- Followed by:12 members
Hi Vincen,If 5 dollars and 35 crowns is equivalent to 7 pounds, and 4 dollars and 4 pounds is equivalent to 56 crowns, 1 pound and 28 crowns is equivalent to how many dollars?
$7.00
$7.50
$8.50
$9.00
$10.00
The OA is A.
Experts, can you help me here? What are the equations I should set here? Thanks in advanced.
Let's take a look at your question.
Suupose that d represents the dollars, c represents the crowns and p represents the pounds, then according to the question statement, we can write the following equations.
5 dollars and 35 crowns is equivalent to 7 pounds:
$$5d+35c=7p$$
$$\frac{5}{7}d+5c=p ... (i)$$
4 dollars and 4 pounds is equivalent to 56 crowns
$$4d+4p=56c$$
$$\frac{4}{56}d+\frac{4}{56}p=c$$
$$\frac{1}{14}d+\frac{1}{14}p=c$$
Substitute p using eq(i)
$$\frac{1}{14}d+\frac{1}{14}\left(\frac{5}{7}d+5c\right)=c$$
$$\frac{1}{14}d+\frac{5}{98}d+\frac{5}{14}c=c$$
$$\frac{1}{14}d+\frac{5}{98}d=c-\frac{5}{14}c$$
$$\frac{7+5}{98}d=\frac{14-5}{14}c$$
$$\frac{12}{98}d=\frac{9}{14}c$$
$$\frac{14}{9}\times\frac{12}{98}d=c$$
$$\frac{1}{3}\times\frac{4}{7}d=c$$
$$c=\frac{4}{21}d ... (ii)$$
The last thing the question says is, 1 pound and 28 crowns is equivalent to how many dollars?
Let x represents the number of dollars we need to find out then:
$$1p+28c=xd$$
Substitute p from eq(i)
$$\frac{5}{7}d+5c+28c=xd$$
$$\frac{5}{7}d+33c=xd$$
Again substitute c using eq(ii) so that we have have the equation in terms of d,
$$\frac{5}{7}d+33\left(\frac{4}{21}d\right)=xd$$
$$\frac{5}{7}d+11\left(\frac{4}{7}d\right)=xd$$
$$\frac{5}{7}d+\frac{44}{7}d=xd$$
$$\frac{49}{7}d=xd$$
$$7d=xd$$
$$x=7$$
Therefore, Option A is correct.
Hope it helps.
I am available if you'd like any follow up.
GMAT Prep From The Economist
We offer 70+ point score improvement money back guarantee.
Our average student improves 98 points.
We offer 70+ point score improvement money back guarantee.
Our average student improves 98 points.