At first glance, it seems like a good estimate; big numbers make bigger number.
But, this is multiplication, which means big numbers will make an extraordinarily big number, in proportion to the numbers themselves.
If you round 31 3/4 up to 32, you can multiply that by 50. To make the estimate easier, multiply 50 by 2,
50 x 2 = 100
Take the zeros off 50 and 30 to make this a bit simpler, and multiply 5 by 3,
5 x 3 = 15
Add each of the zeros you took off to the 15 to make 1500 (1 zero was taken off 50, and 1 off of 30),
And then add 1500 to that other 100
1500 + 100 = 1600
A good estimate for 50 x 31 3/4 would be 1600, not 800.
Therefore,
No. Brenda's estimate of 800 is NOT a good estimate.
Answer:
We get the value of Principal amount i.e initial investment = $61640
Step-by-step explanation:
Interest rate r = 3.59% or 0.0359
Compounded quarterly n = 4
Future Amount A = 117,300
Time t = 18 years
We need to find initial investment i,e Principal Amount P
The formula used is: 
Putting values and finding P

So, We get the value of Principal amount i.e initial investment = $61640
Consider factors of 42, then if the factors can be added or subtracted.
42 = 42 * 1
42 = 21 * 2
42 = 14 * 3
42 = 7 * 6
Since none of these can be added or subtracted to equal 15, no intergers satisfy these criteria.
.24 = 24/100 = 12/50 = 6/25
The abbreviation for milliliters can be any of those two as both are equally correct and can be used internationally thanks to the SI system.