1) The value of y varies directly with x, and y = 20 when x = 2. Find y when x = 8.
2) The amount of money raised at a school fundraiser is directly proportional to the number of people who
attend. Last year, the amount of money raised for 100 attendees was $2500. How much money will be
raised if 1000 people attend this year?
3) Brady bought an energy efficient washing machine for her new apartment. If she saves about 10 gallons of
water per load, how many gallons of water will she save if she washes 20 loads of laundry?
4) If y varies directly with the square of x, and if y = 4 when x = 3, what is y when x = 2?
5) The value of y varies inversely with x, and y = 4 when x = 3. Find x when y = 6.
6) For the Choir fundraiser, the number of tickets Allie can buy is inversely proportional to the price of the
tickets. She can afford 15 tickets that cost $5 each. How many tickets can Allie buy if each cost $3?
7) If 16 women working 7 hours a day can paint a mural in 48 days, how many days will it take 14 women working
12 hours a day to paint the same mural?
8) Suppose x varies jointly with y and the square root of z. When x = –18 and y = 2, then z = 9. Find y when x =
10 and z = 4.
9) The volume of wood in a tree (V) varies directly as the height (h) and inversely as the square of the girth (g). If
the volume of a tree is 144 cubic meters when the height is 20 meters and the girth is 1.5 meters, what is the
height of a tree with a volume of 1000 and girth of 2 meters?
10) The average number of phone calls per day between two cities has found to be jointly proportional to the
populations of the cities, and inversely proportional to the square of the distance between the two cities. The
population of Charlotte is about 1,500,000 and the population of Nashville is about 1,200,000, and the distance
between the two cities is about 400 miles. The average number of calls between the cities is about 200,000.
(a) Find k and write the equation of variation.
(b) The average number of daily phone calls between Charlotte and Indianapolis (which has a population
of about 1,700,000) is about 134,000. Find the distance between the two cities.