QUESTION:
A battery was charged. When the charging began, it was 23 percent full. After 30 minutes of charging, the battery was 89 percent full. how fast did the battery charge and how long did it take?
Solution :
<u>Given</u>
- Initial amount of charge = 23%
- Amount after charge = 89%
<u>procedu</u><u>re</u>
Let the rate of charging be r .
r = (change in charge level) / (time interval) = (89% - 23%) / (30 min) = 2.2 % per minute
charge = (rate of charging)(time) + (initial charge)
100% = r*t + 23%
100% = (2.2 %/min)t + 23%
Solve for t and get
t = [(100 - 23) / 2.2]
Answer = 35 min
N = 20, r = 15;
n C r = ( n * ( n - 1) ( n - 2 ) ... ( n - r + 1 )) / r ! =
20 C 15 = (20 * 19 * 18 * 17 ......8 * 7 * 6) / (15 * 14 * 13 ...* 5 * 4 * 3 * 2 * 1) =
= 15,504
Answer:
They can choose 15 questions in 15,504 ways.
To convert a mixed fraction into an improper fraction, we must follow some steps.
First, we take the whole part and multiply it by the denominator of the fraction.
In this case, we take 2 and multiply it by 8.
Now we add the numerator:
16+3=19
The denominator stays the same:
Hope it helps! :)
Answer:
Step-by-step explanation:
hello :
y = 4x - 5 means : 4x-y=5
y - 3 = 5(4-X) equivalent : y-3 = 20 -5x means : 5x+y =23
