Question: K Rounded to the Nearest Tenth

Comment on K Rounded to the Nearest Tenth

I got this right, but I think for the wrong reason.

When you round to the "nearest tenth" in a number with 3+ numbers after the decimal, do you only round based the unrounded hundredths place? It seems like 4.749 would round up to 4.75, which would round up to 4.8. I thought that any number y greater than 4 would round it up, so that x would have to be greater or equal to 4.

Thanks in advance :)
greenlight-admin's picture

Great question!

When we round to the nearest tenth, then we must examine ONLY the hundredths digit to make our decision to round up or round down.

So, for example, to round 4.749 to the nearest tenth, we examine the hundredths digit, which is 4, so we round down.

Here's why. When it comes to rounding to the nearest tenth, the question is really "Is 4.749 closer to 4.7 or 4.8?"

Well, 4.75 is squarely in the MIDDLE of 4.7 and 4.8. So, since 4.749 is less than 4.75, we know that it is closer to 4.7, which means we must round down.

First, thanks for these great videos and website

Now, in this case how come 9 in the thousandth be more than 4 in the hundredth. I understand, please correct me if I am wrong, that when it comes to decimals, value is reversed, tenth is bigger than hundredths, and hundredths are bigger than thousands. thanks for your time
greenlight-admin's picture

If we want to round a decimal to the nearest TENTH, we must only examine the digit in the HUNDREDTHS position.

So, for example, to round 4.138 to the nearest TENTH, we must only examine the digit in the HUNDREDTHS position. That is, we examine the digit 3. Since 3 is less than 5, we round 4.138 DOWN to 4.1

Likewise, to round 8.371 to the nearest TENTH, we must only examine the digit in the HUNDREDTHS position. That is, we examine the digit 7. Since 7 is greater than or equal to 5, we round 8.371 UP to 8.4

Does that help?

Indeed, although I've never seen a problem like this except on the GRE, I am glad that you talked us through why X must be < 5. It was clear the answer was D, but it didn't come to my mind to actually factor in why x had to be less than 5.

When doing a problem like this on the test and knowing the answer is D, should we still double check?
greenlight-admin's picture

Good question!!

If you 100% know that the answer is D, then you don't need to double-check.

HOWEVER, if it's the case that, while answering practice questions, you "knew" the answer was D but you were wrong (on more than 1 occasion), then you might consider double-checking.

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