Acompany has two types of machines, type r and type s. operating at a constant rate, a machine of type r does a certain job in 36 hours and a machine of type s does the same job in 18 hours. if the company used the same number of each type of machine to do the job in 2 hours, how many machines of type r were used?
a. 3
b. 4
c. 6
d. 9
e. 12

The number of machines to complete job in 2 hours is 6.

Step-by-step explanation:

Using the relation of the rate of each one machine and knowing that adding up both rates.

Rate R =  'x' is the job

Rate S =  'x' is the job

So, using the equation of rates

Rate total is going to be a job in 2 hours so =

adding up

 factoring the x

 simplifying

x=

x= 6

.

step-by-step explanation:

hello,

b) 62.47% of the students are between 14 and 18 years old.

step-by-step explanation:

mean = 15 and standard deviation = 2

student between 14 to 18

formula used z-score

for age 14 , z score

using z-table , p(z> -0.5)=0.3085

for age 18 , z score

using z-table , p(z< 1.5)=0.9332

p(-0.5< z< 1.5)=0.9332-0.3085 = 0.6247

thus, 62.47% of the students are between 14 and 18 years old.

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