# SAT Math Multiple Choice Practice Question 519: Answer and Explanation

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**Question: 519**

**18.** If a, *b, c,* and *d* are consecutive multiples of 5, and *a* < *b* < *c* < d, what is the value of (*a* – *c*)(*d* – *b*)?

A. –100

B. –25

C. 0

D. 50

E. 100

**Correct Answer:** A

**Explanation:**

**A** Because it is much easier working with numbers than with variables, let's plug in some consecutive multiples of 5. Let's say that *a* = 5, *b* = 10, *c* = 15, and *d* = 20. The question then asks for the value of (*a* – *c*)(*d* – *b*). Using the numbers you just plugged in, this becomes (5 – 15)(20 – 10), or (–10)(10), which equals –100.