No more than 33 texts a month
you know the total amount spent, you know the total of the bill without texts
45=39.99+.15t
Answer: d. The helicopter rotor will spin 36,000 times in 1 hour
Step-by-step explanation:
Option A is wrong because in 40 minutes the rotor will spin:
= 40 * 600
= 24,000 times
Option B is wrong because we cannot know the number of times the rotor will spin before being lifted off of the ground with the details given.
Option C is wrong because in 3 hours the rotor will spin:
= 600 * 3 * 60 minutes
= 108,000 times
Option D is correct because in 1 hour the rotor will spin:
= 600 * 1 * 60 mins
= 36,000 times
Short Answer: 18 minutes
Remark
The answer to this problem is less than the smallest time of the two people working together. that fact lets out C and D (38 minutes and 75 minutes). Now you have to choose 15 minutes and 18 minutes. There's a method. No guessing needed.
Givens
Let the time for Sophie = S
Let the time for Simon = M
Let the job to completion = 1
S = 45 minutes
M = 30 minutes
Step One
Convert minutes to hours.
45 minutes = 45 / 60 = 3/4 hour = 0.75 hour
30 minutes = 30 / 60 = 1/2 hour = 0.50 hour
Step Two
Set up the Equation
The formula is a form of job / hour.
Let the time = t that they both have to work
job = 1 in these problems.
1/S + 1/M = 1/t
1/0.75 + 1/0.5 = 1/t
Solve
1 ÷ 0.75 = 1.33333
1 ÷ 0.5 = 2
1.3333 + 2 = 3.33333
3.3333 = 1 / t Multlply both sides by t
3.3333*t = 1
t = 1 / 3.333333333
t = 0.3 of an hour
1 hour = 60 minutes
0.3 hours = x Cross Multiply
x = 60 * 0.3
x = 18 minutes
Answer working together it took them 18 minutes <<<<<
You put 4 in the X
1/2(4)+5y-10<0
2+5y-10<0
-8+5y<0
5Y<8
Y<8/5
