Question

a charter bus travels 210 miles in 3 1/2 hours. assume the distance traveled is directly proportional to the time traveled. write and solve a direct variation equation to find how far the bus travel in 6 hours.

Answer 1

The constant of variation is 60 miles.

Direct variation formula: y = kx

y = 210
x = 3 1/2 miles 
k = ?

k = y/x
k = 210 / 3 1/2 miles

*convert mixed fraction into a simple fraction
3 1/2 = (3*2+1)/2 = 7/2
k = 210 ÷ 7/2

Remember the rule of dividing fractions: multiply the 1st fraction by the reciprocal of the 2nd fraction.
1st fraction = 210 ⇒ 210/1
2nd fraction = 7/2 ⇒ reciprocal = 2/7

k = 210/1 * 2/7 = (210*2)/(1*7) = 420/7 = 60

The constant of variation is 60 miles.

To check: 
y = kx
y = 60 (3.5)
y = 210 miles

Answer 2

We set up an equation: 210 miles/ (3 1/2 hours)= ? miles/ 6 hours

Cross multiply:
? miles* 3 1/2 hours= 210 miles* 6 hours
⇒ ? miles= 210 miles* 6 hours/ (3 1/2 hours)= 360 miles.

The bus would travel 360 miles in 6 hours~