Please help me with these math problems.
#1 Matt subtracted 1.9 from 20.8 and got 1.8. Explain why this is not reasonable?
#2 Explain why it is easier to find 10 minus 1.9 mentally than with paper and pencil.
#3 On May 27, 2001, a high school student ran a mile in 3 minutes 53.43 seconds. This broke the previous U.S. record of 3 minutes 55.3 seconds set in 1965. The world record in 2001 was 3 minutes 43.13 seconds.
How much faster is:
the 2001 U.S. record than the 1965 U.S. record?
the world record than the 1965 US record?
the world record than the 2001 US record?
Please show step by step. Thanks.
Tim -- please attempt to solve these problems yourself.
If you post your answers here, we'll be glad to check them.
i was in 5th grade last year and believe me its EASIER than you will think it is!! ;)
Well Tim,
It's actually very easy if you think abou it :)
No. 1
- Is obviously not reasonable right?
The real answer is really 8.9, very diff from 1.8 right?
Try doing the rest on your own and if you need any help just let us all know :) I am sure we will all be able to help!
195 divide by 13
#1: To determine if Matt's calculation is reasonable, we can subtract 1.9 from 20.8 ourselves.
- Step 1: Subtract the whole numbers. 20 - 1 = 19.
- Step 2: Subtract the decimal parts. 0.8 - 0.9 = -0.1.
Therefore, when we subtract 1.9 from 20.8, we get 19.7, not 1.8. Matt's answer of 1.8 is not a reasonable result.
#2: Finding 10 minus 1.9 mentally is easier than using paper and pencil because it involves a simpler subtraction problem.
- Step 1: Subtract the whole numbers. 10 - 1 = 9.
- Step 2: Subtract the decimal parts. 0.0 - 0.9 = -0.9.
The result is 9.1, which means that mentally subtracting 1.9 from 10 is easier since you only need to subtract the decimal part.
#3:
To find how much faster:
- the 2001 U.S. record is compared to the 1965 U.S. record, we subtract the times of both records.
- the world record is compared to the 1965 U.S. record, we subtract the times of both records.
- the world record is compared to the 2001 U.S. record, we subtract the times of both records.
For each comparison, we'll convert the times into seconds to make the calculation easier.
- 2001 U.S. record: 3 minutes 53.43 seconds = 3 * 60 + 53.43 = 180 + 53.43 = 233.43 seconds.
- 1965 U.S. record: 3 minutes 55.3 seconds = 3 * 60 + 55.3 = 180 + 55.3 = 235.3 seconds.
- World record: 3 minutes 43.13 seconds = 3 * 60 + 43.13 = 180 + 43.13 = 223.13 seconds.
To find the differences:
- The 2001 U.S. record is faster than the 1965 U.S. record by subtracting: 235.3 - 233.43 = 1.87 seconds.
- The world record is faster than the 1965 U.S. record by subtracting: 235.3 - 223.13 = 12.17 seconds.
- The world record is faster than the 2001 U.S. record by subtracting: 233.43 - 223.13 = 10.3 seconds.
Therefore:
- The 2001 U.S. record is 1.87 seconds faster than the 1965 U.S. record.
- The world record is 12.17 seconds faster than the 1965 U.S. record.
- The world record is 10.3 seconds faster than the 2001 U.S. record.