Question

Find 51 • 49 using mental math.

2491


2499


2009


2509

Answer 1

2499

Explanation:

Here's one mental approach:

51*49

(50+1)(50-1)

(a+b)(a-b)=a²-b²

(50+1)(50-1)=50²-1²

2500-1

2499

Or you could say (51*50)-51 = 2550-51 = 2499

Answer 2

51

49

x____

459

2040<--- add zero place holder

+______

2499 is your answer