estimated around 5,000
I think it means to do the work and then estimate it. But it could also be estimate the divisor and dividend and then do the work after those two numbers are estimated.
25x80 < 28x87 < 30x90 --> 2000 < 28x87 < 2700?
find each product
60 x 50 = 3000
3 x 5 = 15
if you subtract each product from the next larger product you will end up with a wrong answer
In your example, the easiest way to estimate the product would be to round each factor to the nearest 10, 100, 1,000 or whatever the factors are. So, for 6,893 * 556, round to 7,000 * 600 to get an estimate. Since both numbers are rounded up, you know your estimate will be high, but this is an easy way to get a close answer. To be specific here, 7,000 and 600 would be multiplied to get 4,200,000. You multiply the first digits together, and then add the total number of zeroes in each rounded number to your answer.
46.78-18.55 and estimate each sum or difference = 28.23