Final answer:
To estimate the product of 77 times 21, the numbers are rounded to the nearest ten and multiplied, resulting in an estimate of 1600. The correct answer from the given options is b) 80 x 20.
Step-by-step explanation:
The question asks to estimate the product of 77 times 21. The first step is to round each number to the nearest ten, so 77 approximately equals 80, and 21 is approximately equal to 20. Then we multiply the rounded numbers: 80 times 20 equals 1600. So, the best estimate for the product of 77 times 21 would be closest to 1600.
Looking at the given options:
- a) 70 x 35 = 2450
- b) 80 x 20 = 1600 (This is our estimate.)
- c) 80 x 40 = 3200
- d) 60 x 20 = 1200
Therefore, the correct answer is b) 80 x 20.