7th Grade Math Help!

Question

I've been sitting at my desk for hours trying to figure this out to help my son in the 7th grade. He's a remote student with no access to a teacher, hence, why I need assistance. I managed to answer the first question; answer 63,360 inches, however, I cannot get past 2 and 3. Do I need to factor 776.1 anywhere in question 2 or 3? Here are my notes...

For question 2:

C = 2 π r

C = 2 x 3.14 x r

C = ________ inches

For question 3:

C = π d = 3.14 x _____

C = __________ inches

Susan has a new mountain bike. For each mile that she rides her bike, her front tire rotates one complete turn approximately 776.1 times.

1. If one mile equals 5280 feet, how many inches are in one mile?
2. What is the circumference, in inches, of the front tire of Susan’s bike?
3. What is the diameter, in inches, of the front tire of Susan’s bike?

Answer 1

C = 6.28r inches

C= 3.14d inches

C = the circumference of a circle with radius r and diameter =d =2r

1 mile = 5280 feet = 12(5280) = 63,360 inches

there's 12 inches in 1 foot.

for one mile, her front tire rotates about 776.1 times.

Circumference of the front tire = 63,360/776.1= 81.64 inches

= 5280/776.1 = about 6.8 feet

so the diameter of the front wheel= 6.8/3.14159 = 2.166 feet

radius = 1.083 feet

the diameter of the front tire = 81.64/3.14159 = about 26 inches

radius = about 13 inches = about 1.083 feet

check the answer by measuring a bicycle wheel. compare it to a chart for bicycle sizes: 26 inch fits a rider height of 5'4" to 6'2"

Answer 2

Looks like the sequence of questions kind of guide you to the answer.

1 mile = 5,280 ft; 5,280 ft x 12"/ft = 63,360 " in 1 mile. Think of the track the tire makes. It turns 776.1 times to go 63,630 ", so the circumference of the tire must be 63630/776.1 = 81.639" (answer to #2)

Circumference = pi x diameter -> 81.639 = 3.14159 x d -> d = 81.639/3.14159 = just under 26". (#3)