Using the rate formula:  Distance = Rate x Time,

Since Jack’s speed was 7 mph, Jack completed the course in 3 hours

21 = 7 x t

t = 3

Sam’s speed was half of Jack’s speed: 7/2 = 3.5

21 = 3.5 x t

t = 6

Therefore it took Sam 3 hours longer to run the course.

Algebraic solution:  First, convert minutes to hours. 

60/15 = 4, so there are 4 15-minute increments in each hour. Therefore, 4x ounces of water are collected each hour.  Multiply by h to get 4xh as the solution

Plug-in method:  Just choose numbers.

x = 2

h = 3

If 2 ounces drip in 15 minutes, how many ounces will drip in one hour?

2/15 = x/60

15x = 120

x = 8

If 8 ounces drip in one hour, how many ounces will drip in 3 hours? (remember we chose that h = 3)

3 x 8 = 24    

This is the answer we are looking for.

Plug x = 2, and h = 3 into each answer choice, to determine which will work.  Remember you must plug into every answer choice in case more than one works.  In that case, choose different values for x and h, and plug into only the choices that worked the first time.

If Mark makes 15 snowballs in 30 minutes, he can make 30 snowballs in an hour. Working together they can 50 snowballs in one hour. 150 snowballs divided by the amount they can make in one hour (50) will give us the total time it will take them to make 150 snowballs. In this case, 3 hours.

We first use the data for car X to conclude that car X went 40 miles (4gallons*10mi/gallon). We then use 40 miles for car Y, and divide 40 by 8, to give us 5 gallons of gas.

Since the kids are trying to do their chores in one fifth of the time, they need five times as many people. Since they have two, five times as many would be ten. We subtract the two of them and that would mean they need 8 more people, giving us answer 8.

1 gallon = 3.785L = 3785mL, half of the tank = 250*3785 = 946,250mL. To find the minutes, 946250mL/(100mL/min) = 9462.5min. Since 1 day=24hr*60min=1440min, the number of days =94625min/(1440min/day)=6.5 days

15 + 25 = 40 minutes. 40 minutes is 2/3 of an hour. Distance = rate x time. Using this formula, we have 4 = (2/3) r. To solve for r we multiply both sides by (2/3). r = 6

Distance traveled = mph x hour

60mph x 2hours + 55mph x 1.5 hours + 30 mph x 45 minutes (or .75 hours) =

120 miles + 82.5 miles + 22.5 miles = 225 miles

1200 ft per hour becomes 20 ft per second (divide 1200 by 60 because there are 60 minutes in an hour). 180/20 is 9, giving 9 minutes to travel 180 ft.

The best way to find speed is to divide the distance by time. Since time is given in minutes we must convert minutes to hours so that our units match those in the answer choices. (3miles/15min)(60min/1hr)=12miles/hr;  Remember when multipliying fractions to multiply straight across the top and bottom.