Because 259 is close to 260, 259 times 89 is about 260 times 80. Is that right or wrong?

Because 259 is close to 260, 259 times 89 is about 260 times 80. Is that right or wrong?


3 and 4 are close to 5, 3 times 4 and 5 times 5, the difference is very big = = if 260 is such a big number, how big is the error