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when ella does 13 push-ups and 7 sit-ups, it takes a total of 60 seconds. in comparison, she needs 96 seconds to do 13 push-ups and 19 sit-ups. how long does it take ella to do each kind of exercise?

it takes ella seconds to do a push-up and seconds to do a sit-up.

The answer is:

It takes Ella 3 seconds to do a push-up and 3 seconds to do a sit up.

To find how many seconds Ella took to do a push-up and a sit-up we must write two equations using the given information.

Let be "x" the time needed to push-ups and "y" be the time needed to do sit-ups.

So, writing the equations we have:

First equation,

If she can do 13 push-ups and 7 sit-ups in 60 seconds, we have:

Second equation,

If she can do 13 push-ups and 19 sit-ups in 96 seconds, we have:

Now, creating a system of equations, and using the reduction method to solve it, we have:

Multiplying the first equation by -1, we have:

Then, substituting "y" into the first equation, we have:

Hence, we have that It takes Ella 3 seconds to do a push-up and 3 seconds to do a sit up.

Have a nice day!

ok

step-by-step explanation:

percentage - 25%

probability - 0.25

we know,

total amount of students in class = 20

total boys = 10

total girls = 10

no of girls who wear glasses = 10/2 = 5

probability of choosing a girl with glasses is =

number of girls wearing glasses/total number of students in the class = 5/20

thus, percentage of selecting a girl wearing glasses will be

= 5/20 × 100

= 5 × 5

25%

therefore,

probability will be 0.25

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