Look at how Mason estimated the product by rounding the two-digit number to the nearest 10. Use his method to estimate 77 times four. Use his method to estimate 63 times seven.
First, let’s look at Mason’s method. He says 52 times seven is close to 50 times seven. Five tens times seven equals 35 tens. Then he says I estimate that 52 times seven will be close to 350.
Mason started off with the problem 52 times seven. He knew that 52 was closest to 50. And from there, he said 50 is equal to five tens. If you multiply five times seven, it equals 35. Five tens times seven is then equal to 35 tens. And 35 tens is equal to 350.
Let’s use the same process to solve our two problems. We have 77 times four. 77 is closest to 80. 80 is equal to eight tens. We can multiply that by four. Eight tens times four equals 32 tens. 32 tens equals 320. So we can say that 77 times four is close to 320. It will be about 320.
We have one more problem to solve: 63 times seven. What can we round 63 to? 63 is closest to 60. 60 is equal to six tens. Six tens times seven equals 42 tens. And 42 tens equals 420. 63 times seven will be close to 420. Or we can say 63 times seven will be about 420.