Please check the problem in the main article once again. The problem was correctly solved at the top. Then as a check on the answer simple 100’s and tens were used. I was trained in this method 60 years ago. Scientists use it, engineers use such a check, businessmen use it. IT IS A METHOD USED TO CHECK ONES INITIAL COMPUTATION. IT IS NOT THE COMPUTATION ITSELF. IT IS NOT INTENDED TO REPLACE TRUE AND ACCURATE COMPUTATION BUT TO CHECK.
What makes you think I didn’t understand that?
All I’m saying is that I naturally made a more accurate estimate—which this lesson would be training kids away from using.
I wasn’t around for training 60 years ago, but I never had to be taught to estimate as a check on my work.