Answer:
755,160 ways
Explanation:
We're told that 31 cars are in a race.
Considering the order in which the cars can finish in the top 4 positions, any of the 31 cars can finish in the first position, any of the remaining 30 cars can finish in the second position, any of the remaining 29 cars can finish in the third position and any of the remaining 28 cars can finish in the fourth position, so the different numbers of ways can be determined as seen below;
Answer:
Levi's dad takes 1.67 hours to wash the car by himself
Step-by-step explanation:
* Lets explain how to solve the problem
- Levi takes 2.5 hours to wash his dad's car alone
- Levi and his dad take 1 hour to wash the dad's car together
∵ Levi takes 2.5 hours to wash the car alone
∴ The rate of Levi is 1/2.5 car/hr
∵ His dad takes x hours to wash the car alone
∴ The rate of his dad is 1/x car/hr
∵ They working together for 1 hour to wash the car
- The equation of the work is rate of Levi × t + rate of his dad × t = 1
∵ t is the time of working together
∵ t = 1 hour
∴
- Multiply both sides by 2.5x to cancel the denominators
∵
∵ 1 × (2.5x) = 2.5x
∴ x + 2.5 = 2.5x
- Subtract x from both sides
∴ 2.5 = 1.5x
- Divide both sides by 1.5
∴ x = 5/3 ≅ 1.67
∵ x is the the time of his dad to wash the car alone
∴ Levi's dad takes 1.67 hours to wash the car by himself