As Mike (above) said:
"...but it is still a good idea to estimating where you should be on the number line."
The seemingly endless repetition and practice problems from my math instructors all the way from early grades through college actually was useful in making the estimation part of problem-solving almost automatic. In retrospect, it was NOT busywork.
From my high-school physics teacher, who also taught the advanced math classes, I also learned to always put the units in along with the numbers, so you can make sure your doing the arithmetic to the right things in the process. In addition the much-hated instruction to "Show Your Work" is a good thing as well, so you can see where you went wrong. My grandkids only grudgingly wanted me to help with math homework because of the busywork aspects they didn't like, but usually ended up with "NOW I get it" after working that way for a short time.
My two cents.....
--ShopShoe