What is the Number of Positive Divisors of the Form (4n + 2) of Integer GMAT Problem Solving

Question: What is the number of positive divisors of the form (4n + 2) of integer 240, where n is an integer ≥ 0 ?

(A) 4
(B) 8
(C) 10
(D) 11
(E) 12

Correct Answer: A
Solution and Explanation:

Approach Solution 1:
Some observations:
4n is divisible by 4 for all integer values of n
So, 4n + 2 is NOT divisible by 4
But 4n + 2 IS divisible by 2
So we're looking for divisors of 420 that are EVEN but NOT divisible by 4

240 = (2)(2)(2)(2)(3)(5)
We can see that the following divisors are EVEN but NOT divisible by 4:
(2)
(2)(3)
(2)(5)
(2)(3)(5)

Evaluate to see that 2, 6, 10 and 30 are the only positive divisors in the form (4n + 2)

Approach Solution 2:

Since 240= 2^4*3*5
Therefore, the total number of divisors= (4+1)(2)(2)= 20 out of these 2,6,10 and 30 are of the form 4n+2.
So option A is correct.

Approach Solution 3:

We can write 240 as 2^4.3^1.5^1
But we want divisors of the form 4n+2
That is, we want even divisor of the form 2(2n+1) and n ⩾ 0
The divisor id 2 (when n=0) or divisor are odd multiples of 2
So the divisors are 2, 6, 10 and 30.

Hence, 4 is the correct answer.

“What is the number of positive divisors of the form (4n + 2) of integer”- is a topic of the GMAT Quantitative reasoning section of GMAT. To solve GMAT Problem Solving questions a student must have knowledge about a good amount of qualitative skills. GMAT Quant practice papers improve the mathematical knowledge of the candidates as it represents multiple sorts of quantitative problems.

Suggested GMAT Problem Solving Samples

Fees Structure

CategoryState
General15556

In case of any inaccuracy, Notify Us! 

Comments


No Comments To Show