Nina can ride her bike 63,360 feet in 3,400 seconds, and sophia can ride her bike 10 miles in 1 hour. What is nina’s rate in miles per hour if there are 5,280 feet in a mile? Which girl bikes faster?

Nina's rate in MPH:  12.706 miles per hour

Nina is faster than Sophia.

Step-by-step explanation:

For this problem, we will convert feet per second into miles per hour, and then compare Nina's rate to Sophia's rate.

We are given Nina rides at 63360 feet in 3400 seconds.  To convert this to miles per hour, we need to know that there are 5280 feet in 1 mile, and 3600 seconds in 1 hour.  Now that we now these conversions, let's find the rate in miles per hour.

(63360 feet / 3400 seconds) * (1 mile / 5280 feet) * (3600 seconds / 1 hour) = 12.706 miles per hour.

So we know that Nina rides her bike at 12.706 miles per hour and are given that Sophia rides her bike in 10 miles in 1 hour.

With this, we can say Nina rides faster than Sophia by 2.706 miles per hour (12.706 - 10).

Cheers.

let x and 400 - x be the two numbers.  

==> 0.80x + 0.85(400 - x) = 400 - 68 from the statement of the problem.  

< ==> 0.80x + 0.85(400 - x) = 400 - 68  

==> 340 - 0.05x = 332  

< ==> -0.05x = -8 ==> x = 160, the first number ==> 400 - x = 240, the second number.