Hi,
I got this question on a MGMAT CAT exam. I don't really understand the explanation they provided to the problem...Can anyone help shed some light on this? Or perhaps an alternate method to solve?
Thanks
Joan, Kylie, Lillian, and Miriam all celebrate their birthdays today. Joan is 2 years younger than Kylie, Kylie is 3 years older than Lillian, and Miriam is one year older than Joan. Which of the following could be the combined age of all four women today?
A)51
B)52
C)53
D)54
E)55
Anwser:
D
t may be easiest to represent the ages of Joan, Kylie, Lillian and Miriam (J, K, L and M) on a number line. If we do so, we will see that the ages represent consecutive integers as shown in the diagram.
Since the ages are consecutive integers, they can all be expressed in terms of L: L, L + 1,
L + 2, L + 3. The sum of the four ages then would be 4L + 6. Since L must be an integer (it's Lillian's age), the expression 4L + 6 describes a number that is two more than a multiple of 4:
4L + 6 = (4L + 4) + 2
[4L + 4 describes a multiple of 4, since it can be factored into 4(L + 1) or 4 * an integer.]
54 is the only number in the answer choices that is two more than a multiple of 4 (namely, 52).
The correct answer is D.
Mgmat CAT PS question
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The ages are all close together.GmatKiss wrote:Joan, Kylie, Lillian, and Miriam all celebrate their birthdays today. Joan is 2 years younger than Kylie, Kylie is 3 years older than Lillian, and Miriam is one year older than Joan. Which of the following could be the combined age of all four women today?
· 51
· 52
· 53
· 54
· 55
The answer choices imply that the sum of the 4 ages is between 51 and 55, inclusive.
Since 52/4 = 13, the average age must be around 13.
Let J=13.
Since Joan is 2 years younger than Kyle, K=15.
Since Kyle is 3 years older than Lillian, L=12.
Since Miriam is 1 year older than Joan, M=14.
Sum = 13+15+12+14 = 54.
The correct answer is D.
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Here is the explanation for official answer...G- Unit30 wrote:Joan, Kylie, Lillian, and Miriam all celebrate their birthdays today. Joan is 2 years younger than Kylie, Kylie is 3 years older than Lillian, and Miriam is one year older than Joan. Which of the following could be the combined age of all four women today?
Let assume the ages of Joan, Kylie, Lillian, and Miriam are J, K, L, and M, respectively.
Hence, J = (K - 2), K = (L + 3), M = (J + 1)
Expressing them all with respect to L only,
- K = (L + 3), J = (L + 1), and M = (L + 2)
Hence, the answer must be 2 more than a multiple of 4.
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THANK YOU that helps (in other words- (4L + 6)= 2(2L+3) only time we get an integer value for L is when it is 54Anurag@Gurome wrote:Here is the explanation for official answer...G- Unit30 wrote:Joan, Kylie, Lillian, and Miriam all celebrate their birthdays today. Joan is 2 years younger than Kylie, Kylie is 3 years older than Lillian, and Miriam is one year older than Joan. Which of the following could be the combined age of all four women today?
Let assume the ages of Joan, Kylie, Lillian, and Miriam are J, K, L, and M, respectively.
Hence, J = (K - 2), K = (L + 3), M = (J + 1)
Expressing them all with respect to L only,Hence, combined age of all four women = (L + 3) + (L + 2) + (L + 1) + L = (4L + 6) = (4L + 4) + 2 = (Some multiple of 4) + 2
- K = (L + 3), J = (L + 1), and M = (L + 2)
Hence, the answer must be 2 more than a multiple of 4.