1. justin’s car can travel 77.5 miles using 3.1 gallons of gas.
at this rate, how far, in miles, can justin travel using 8.2 gallons of gas?
2. the marching band has 85 members. there are 15 more girls than boys in the band. how many boys are members of the marching band?
explain and show the ; w;

1)  Write this as a ratio...

77.5 miles / 3.1 gallons = x miles / 8.2 gallons

Solve for x... multiply by 8.2 gallons on both sides (that cancels it on the right) side of the equation.

8.2 gallons * 77.5 miles / 3.1 gallons = x
635.5/ 3.1 = x
211.83 miles = x

Justin travels 211.83 miles on 8.2 gallons of gas

2) If we let boys = b, then girls has to be b + 15 (since there are 15 more girls than boys).  Now together there are 85 members of the band so... boys + girls = 85  and since girls is b + 15, then...

b + b+15 = 85

Now solve for b.  First combine like terms...

2b + 15 = 85

Now subtract 15 from each side (cancels the 15 on the left)

2b + 15 - 15 = 85 - 15
2b = 70

Now divide each side by 2 (cancels 2 on the left)

2b / 2 = 70 / 2
b = 35

So there are 35 boys in the band.

Just FYI, that also means there are 35+15 = 50 girls.  Just so happens that 50 + 35 = 85 so our work checks!

 

Distance/fuel=ratio 77.5/3.1 is proportional to xdistance/8.2 77.5/3.1=x/8.2 multiply both sides by (3.1*8.2) 635.5=3.1x divide both sides by 3.1 205=x 205 miles 2. easy peasy one way is boys+15=girls boys+girls=85 boys+boys+15=85 minus 15 2boys=70 divide 2 boys=35