rounding 1.139 to nearest hundredth

Question

my son had a test question to round 1.139 to the nearest hundredth. He answered w/ 1.140 and got it wrong. Teacher said it should be 1.14. Isn't 1.14 and 1.140 the same?

Answer 1

Not exactly. See, putting that 0 on the end there has people looking at the thousandths and thinking that that's what the thousandths are, but it's not. It was modified for the purposes of rounding.

 

Let's use pi as an example. It's most often rounded off to 3.14, but see, if we write it out a bit further, it becomes 3.14159. When we round pi off to the nearest hundredth, we don't say 3.140

 

Another way to look at it would be how we would say it. Looking at 1.14, we would read out "one and fourteen hundredths," not "one and one hundred forty thousandths." That way leads to madness if you add on more zeroes to look like 1.14000000000. All those zeroes are extraneous; leave them out if they aren't necessary.

Answer 2

1.14 and 1.140 are equal in value but 1.14 means a number was rounded to the hundredths place while 1.140 means that a number was rounded to the thousandths place

example: round 1.1398 to the nearest thousandth

the 8 means round up so the 9 becomes 10 and you put down the 0 and carry the 1 and add it to the 3 to become 4  

the answer is 1.140, not 1.14

personally, I think the teacher should at least have given your son partial credit for knowing to change the 3 to a 4