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Front End Estimation can be confusing before you understand it. There are two simple steps for front end estimation: add the digits of the two highest place values, insert zeros for the other place values. Now let's put that into us for your question!189-643 =(1 & 8 are the first two digits for 189 ... 6 & 4 are the first two digits for 643)18_ - 64_ =(Fill in zeros for the place values you have emptied)180-640= -460-460
643 - 189 = 454
explain how you would estimate to subtrac 189 from 643
189 rounded up to the nearest 100 number would be 200; 200 subtracted from 643 = 443 , 200 - 189 454
640 - 190 = 450
1285
Does subtraction come to mind, try it, you can do it, good luck!
643 is a prime number. So its factors are 1 and 643.
75 of 643 is 48,225. 75% of 643 is 482.25