Question

What is the best estimate for the product of 289 and 7

Answer 1

I was taught to round it up to the nearest ten, then multiply it like this,
289, rounded up is 290, then seperate the number, (200 + 90)

200 X 7 = 1400 (multiply the numeral, then add the zeros)
90 X 7 = 630 (repeat the same process)

1400 + 630 = 2030 (actual answer = 2023)

Answer 2

I would estimate it as (300 x 7) = 2100

Then I would subtract (11 x 7) + 77 from that to get the exact answer of 2023

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I didn't use a calculator or paper. The 'trick' is to notice that 289 = (300 - 11)