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Dahasolnce [82]
3 years ago
13

Q7.

Mathematics
1 answer:
VLD [36.1K]3 years ago
3 0

Answer:

10

Step-by-step explanation:

Let c = sum of ages of all children.

mean age of all children = c/15 = 7

c = 15 * 7 = 105

The sum of the ages of all children is 105.

Let b = sum of ages of the 9 boys.

mean age of boys = b/9 = 5

b = 9 * 5 = 45

The sum of the ages of the boys is 45.

The sum of the ages of the girls is c - b.

c - b = 105 - 45 = 60

The number of girls is 15 - 9 = 6

mean age of girls = (sum of ages of the girls)/(number of girls) =

= 60/6 = 10

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<h2>The crime gets cleaned up at 2:00 PM</h2>

Step-by-step explanation:

Let the work be w.

Batman can clean up all of the crime in Gotham City in 8 hours working alone.

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Robin can do the same job alone in 12 hours.

\texttt{Rate of Robin,}r_r=\frac{W}{12}

Robin starts work at 8:00 AM and Batman Joins at 10:00 AM.

Let the time of completion of work after Batman's joining be t.

We have time of working of Robin = t + 10:00 -8:00 = t + 2

So

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After 4 hours of 10:00 Am work gets completed.

Time = 10:00 AM +  4 hours =  2:00 PM

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Step-by-step explanation:

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