Question

A rectangle has a length of 9.00 inches and a width of 4.25 inches. What is the area in square inches? Round to the correct significant digits.

Numerical Answers Expected!

Answer 1

Do you remember the area formula for a rectangle?

Answer 2

l*w*h?

Answer 3

No, that would be volume of a (rectangular) prism; if you want area, it's just l * w.:-)

Answer 4

so it would be 38.25?

Answer 5

Almost; That's the correct numerical value, but your answer isn't rounded to the correct number of significant figures (as the question requires). If you look at the original numbers you were given (9.00 and 4.25), how many significant figures are there? :-)

Answer 6

digits, not figures.

Answer 7

oh so would it be 9*9*4.25*4.25?

Answer 8

No, the answer you came up with -- 38.25 -- is very close to the answer but it has 4 significant digits. The original numbers we were given -- 9.00 and 4.25 -- have how many significant digits? :-)

Answer 9

2?

Answer 10

How many digits do you see in each number (ignoring the decimal point for now)?

Answer 11

3 in each

Answer 12

Correct; that means those numbers have 3 significant digits. Thus, the answer that we want should also have 3 significant digits. The answer you came up with -- 38.25 -- has 4 significant digits. What should be done in order to write it with 3 significant digits? :-)

Answer 13

38.250?

Answer 14

You've now increased it to 5 significant digits. :-/

We want to decrease the number of digits; the thing you want to do here is round 38.25 to the nearest tenth. What do you get when you do that? :-)

Answer 15

Is it 38.2?

Answer 16

@ChristopherToni ?

Answer 17

It should be 38.3 (rounding up to the nearest tenth place). Does that make sense?

Answer 18

OOOOh so thats what it means to round significvatlly?

Answer 19

For the most part. The first thing you had to determine was the number of significant digits you have at the start of the problem. Then when you multiply out your values and get something that has more digits than what you started with, you need to round your answer to the appropriate number of significant digits (which in this case is 3).

I hope that made sense! :-)

Answer 20

Thanks for your help!!, You're a wonderful teacher!!!

Answer 21

Thanks, it was a pleasure helping out again. :-)

Answer 22

See you later (tomorrow) :D