# Math

I an taking the SAT this week and I am so screwed. I keep getting these types(and ratio and probability- tips?) of questions wrong on practices. I basically set up a chart for d(distance/amount of sth), v(speed/rate), and t(time) and try to fill it out. I usually fill it out(except for #2) correctly, but I don't know what to do with the results LOL. Thank you(I feel so dumb right now), and I hope you can provide some tips and explanations, and also some good sites explaining the ratio, probability, and word problem sections.

1. A freight train left a station at 12 noon, going north at a rate of 50 miles per hour. At 1:00pm, a passenger train left the same station, going south at a rate of 60 miles per hour. At what time were the trains 380 miles apart?

2. A man drove to work at an avg rate of speed of 60 miles per hour and returned over the same route driving at an avg rate of speed of 40 miles per hour. If his total driving time was 1 hour, what was the total number of miles in the round trip?

3. If x people working together at the same rate can complete a job in h hours, what part of the same job can one person working alone complete in k hours?

1. t is time after 12 noon

f for freight train
distance f = df = 50 t

p for passenger train
dp = 60 (t-1)

when is dp - df = 300 ?

60(t-1) - 50 t = 380
10 t - 60 = 380
10 t = 440
t = 44 hours
so one day and 20 hours
so 8 am
---------------------------------
total distance = 2d
drove out for time t
drove back for time = 1-t
d = 60 t
d = 40 (1-t)
so
60 t = 40 (1-t)
100 t = 40
t = .4 hour
d = 60*.4 = 24 miles
so
2d = 48 miles round trip
=========================
one man works at 1/(xh) jobs / man hour
so man hours per job = x h
k/(x h) = fraction desired

posted by Damon

## Similar Questions

1. ### Elementary Statistics

SAT math test scores for all students taking the test are approximately normally distributed with mean score of 514 and std. deviation of 118. What is the probability that a randomly chosen student will earn a score above 600 on
2. ### SAT

is there any helpful practice sat tests online other than the college board? i'm taking the test this saturday and i don't feel like i'm ready for it. i have studied the SAT prep book that i have, as much as i can. i especially
3. ### statistics

SAT scores are normally distributed. The SAT in English has a mean score of 500 and a standard deviation of 100. a. Find the probability that a randomly selected student's score on the English part of the SAT is between 400 and
4. ### The SAT

I'm a 7th grader registered for the Duke TIP SAT. What is a good goal for me to set? Average score of a 7th grader taking the SAT?(:
5. ### math

The distriubution of the SAT scores in math for an incoming class of business students has a mean of 580 and standard deviation of 25. Assume that the scores are normally distributed. a. Find the probability that an individual's
6. ### SAT

im taking the Sat's tomorow..what are some great tips??
7. ### English

1. She sat taking notes "on" everything that was said. 2. She sat taking notes "of" everything that was said. ------------- Which one is right? Can we use both 'on' and 'of'? which one is commonly used?
8. ### Statistics

A specially equipped trauma emergency room at a hospital has been in operation for 40 weeks and has been used a total of 108 times. Assuming the weekly pattern of demand for this facility is poisson compute the following -
9. ### Maths

Six friends sat around a circular table. Ann (who is the the banker) sat opposite the consultant. Bob sat opposite Fred. Celia sat on the doctors right. Dave (who is not the consultant) sat opposite the accountant. Emily sat
10. ### statistics

1. Use the following information about a group of college students: Fifty percent are taking Algebra. Sixty percent are taking Biology. Thirty percent are taking both Biology and Algebra. A student from the group is selected at

More Similar Questions