If multiplying a certain number by itself 7 times yields y and 2y = 43

Question

If multiplying a certain number by itself 7 times yields y and 2y = 4374, what is the number?

A. 2187
B. 624
C. 17
D. 3
E. 2

Kurtosis · Answer

x^7 = y
2(x^7) = 4374
x^7 = 2187

x = 3

Answer: D

Abhishek009 · Answer

2y = 4374

Or, y = 2187

So, we can say x^7 will be 2187

Since the units digit is 7 , the units digit of x must be 3

So, 3^7 = 2187
  
Hence, answer will be (D)

surfingpirate · Answer

1) 2y = 4374 => y = 2,187
2) realized that 3^7 or 2^7 would likely be <= to 2187 and 17^7 would be huge
3) Broke up 3^7 so I had 9x9x9x3 = 81x9x3 = 729x3 =  ~2100

So D

JeffTargetTestPrep · Answer

We can let the number = n and create the equation:

n^7 = y

We also have:

2y = 4374

y = 2187

Thus, we have:

n^7 = 2187

Let’s check answer choices to determine a possible value for n. Since n^7 is odd, we can eliminate all the even choices, such as B and E. Next, we see that 17 is too large a value for n: 10^7 is 10000000 and 17^7 is even larger than that. Since 17 (and every value greater than 17) is eliminated, the only possible value is n = 3.

Answer: D

If multiplying a certain number by itself 7 times yields y and 2y = 43

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Problem Solving (PS) Questions

If multiplying a certain number by itself 7 times yields y and 2y = 43

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards