What are the other expressions then I can help
Answer: 70 ft
Step-by-step explanation:
Given
height of book is measured by the function is
when the book is thrown 
The height of the book is 
It depends on what you are trying to calculate but the most common way I go to find percentage is to multiply by the number in decimal for ie. 50% = .5.
If you are looking for a way to do it quickly in your head I always take find out what 10% is like in the case of 100 it would be 10 so if I want to find 15% I know I can find 10% and if I cut what 10% is in half I will find 5% so likewise if I add what 10%+5% I will end up with 15%. For example, 10% of 100 is 10 half of 10 is 5 and 10+5 equals 15. If you need to find something like 20% or 30% I know that I can find 10% and instead of dividing(cutting it in half) I can multiply by 2 or 3. 10% + 10% =20%
I hope it helps, if you have more questions let me know!
Answer:
100 km/hr
Step-by-step explanation:
First Leg:
Speed = 60 km/h
Time = 30 min = 0.5 h
1st leg distance = speed x time = 60 km/hr x 0.5hr = 30 km
Second Leg:
Distance remaining = 80 km - 30 km = 50 km
Time = 30 min = 0.5 h
speed = distance / time = 50 / 0.5 = 100 km/hr
