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3 years ago

The mean mark is 70% there are 30 students 20 of which are boys with a mean mark if 62% what is the mean for girls

Mathematics

1 answer:

Anna007 [38]3 years ago

7 0

Answer:

This problem can be solved by working backwards.

Average of 30 students = 70.

Total marks of all the 30 students = 30x70 = 2100

Out of these 30, average of 20 students = 62

Total marks of these 30 students = 30x62 = 1860

So the total marks of the remaining 10 students = 2100-1860 = 240

Hence the average of the remaining 10 students = 240/10 = 24

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Sarah drove 40 miles per hour. In 3 hours, Sarah drove 120 miles. Which is a valid proportion to represent the problem? StartFra

kaheart [24]

Answer:

120 over 3

Step-by-step explanation:

Distance/time=speed

only other division is distance/speed=time but 120/40 isnt an option

Fractions mean division so 120 over 3 = 120/3

Im twelve years old

5 0

3 years ago

Read 2 more answers

During a week-long dry spell, the water level in a pond decreased by 4 in. Per day, except for two days when it decreased by hal

Helga [31]

Answer:

24 inches.

Step-by-step explanation:

Given:

During a week the water level in a pond decreased by 4 in. Per day,

For two days, it decreased by half that amount = $4\times\frac{1}{2}=2\ inches\ per\ day$

Question asked:

How much did the water level decrease in the pond in one week?

Solution:

As we know, there are 7 days in a week.

Each day water level decreased by = 4 inches

In 5 days, water level decreased by = $4\times5=20\ inches$

<u>For exceptional 2 days:</u>

Each day water level decreased by = 2 inches

In 2 days, water level decreased by = $2\times2=4\ inches$

Water level decreased in whole week = 20 + 4 = 24 inches

Therefore, water level decreased 24 inches in the pond in one week.

7 0

3 years ago

Write a quadratic function f whose zeros are 4 and 3 .

Pani-rosa [81]

F(x) = (x-4)(x-3)

if you put x=4, it makes f(x) 0. if you put x=3 it makes f(x) 0

5 0

3 years ago

How to do linear equations 27, 28,28,30

Mekhanik [1.2K]

#27.
First cross multiply
2 (2a-3) = 3 (a-1)
next use the distribute property on both sides
4a - 6 = 3a - 3
combine like terms, subtract 3a from both sides and add 6 to both sides
a = 3

#28
cross multiply
3x = 4, then divide both sides by 3
x = 4/3

#30
add 1/4 to both sides
3/x = 1/2 + 1/4, find a common denominator for the right side fractions
3/x = 2/4 + 1/4 = 3/4
therefore, x = 4

6 0

3 years ago

three cones have a volume of 192π cm³.Cone A has a radius of 2 cm. Cone B has a radius of 3 cm. Cone C has a radius of 4 cm. fin

andrew11 [14]

9514 1404 393

Answer:

A: 144 cm

B: 64 cm

C: 36 cm

Step-by-step explanation:

The volume of a cone is given by ...

V = (1/3)πr²h

Solving for h, we get ...

3V/(πr²) = h

Filling in the given values, we get ...

3(192π)/(πr²) = h

576/r² = h

Then the heights of the different cones are ...

A: r = 2, h = 576/4 = 144 . . . cm

B: r = 3, h = 576/9 = 64 . . . cm

C: r = 4, h = 576/16 = 36 . . . cm

8 0

3 years ago