# SAT Math Multiple Choice Question 4: Answer and Explanation

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**Question: 4**

**4.**

In the equation above, if a and b are positive integers and is in its simplest reduced form, what is the value of a ?

- A. 2
- B. 9
- C. 18
- D. 40

**Correct Answer:** B

**Explanation:**

B The lowest number that both 8 and 10 are factors of is 40. Convert the fractions to a denominator of 40: + = . There is no factor that 9 and 40 have in common, so the fraction cannot be reduced. The number in place of a in is 9, so the answer is (B). Be careful! The value of b is in (D).