CAT Questions

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Mass of zinc ore = 8000 kg

Mass of metal = 60% of 8000 = 4800 kg

Mass of silver in metal = 3/4 x 4800/100 = 36 kg

Mass of zinc = 4800 - 36 = 4764 kg.

For a triangle, we need 3 non-collinear points. So with 12 points (when all the 12 are such that any three non-collinear is12C3. But among them 8 points are collinear.

If all these 8 points are different we get 8C3 triangles as they are collinear.

In 12C3 triangles, we do not get 8C3 triangles

Therefore, The number of triangles we get = 12C3-8C3 = 164

True, Air is a Mixture.

Air is considered as mixture for the following reasons ;

1. Air can be separated into its components like N2, O2 , Argon and CO2 by the process of fractional distillation of liquid air.

2. Air shows the properties of all the gases present in the atmosphere.
For example : Oxygen is good Supporter of combustion. Hence air also is good supporter of combustion.

3. Air does not have a fixed formula.

4. Air has a variable composition because air at different places contains different amount of gases.

5. Heat or Light energy is neither absorbed nor released when air is prepared physical by mixing required amount of gases .

6. Mixture does have fixed boiling Point. It holds good in case of liquid air.

Two series alternate here, with every third number following a different pattern.
In the main series, 4 is added to each number to arrive the next.
In alternate series, 5 is subtracted from each number t arrive the next number.
Here in the main series 
3 + 4 = 7
7 + 4 = 11
11 + 4 = 15
15 + 4 = 19

In alternate series 
24 - 5 = 19
19 - 5 = 14...

According to the given data,

(V + R)/2 = 24

Now, after joining of Veerender,

V + R + D)/3 = 25.5

Hence, Veerender Age = 3(25.5) - 2(24) = 76.5 - 48 = 28.5 years.

A device which is used to convert light energy directly into electrical energy is called as photovoltaic cell or a solar cell.

Heliostats convert light energy into heat energy.

A thermocouple is a device for measuring temperature.

Given teacher drinks 9 ltr
Let number of boys be 'A'.
Let number of girls be 'B'.
Boy drinks 7 ltr and girl drinks 4 ltr
After class total water consumed = 42 ltr
Then,
9 + 7A + 4B = 42
=> 7A + 4B = 33
By trial and error method,
The only integers which satisfy the equation is A = 3 and B = 3
Therefore, number of girls in the class = 3.