Exams

Hardness can be removed by adding sodium carbonate (washing soda) or by passing the water through an ion-exchange column.

Hardness in water is caused by dissolved magnesium ions and calcium ions. These can get into the water when it comes into contact with limestone and other rocks that contain calcium compounds. This can happen, for example, when rainwater flows over these rocks on its way to a reservoir.

Hardness in water is of two types. They are :

1. Temporary hardness

2. Permanent hardness

1. Temporary hardness:: Temporary hardness is caused by dissolved calcium hydrogen carbonate.

2. Permanent hardness:: Permanent hardness is caused by dissolved calcium sulfate. Unlike temporary hardness, it is not removed by boiling the water.

Clearly, defence is necessary for the safety of the country, which is of prime importance. So, argument I holds. Also, a country can concentrate on internal progress and development only when it is safe from external aggressions. So, argument II does not hold.

Let the Father be x years when he died

Average Age 10 years ago be A

Total Age 10 years ago = 6*A

Total Age after 10 years(Just before father's Death) = 6A + 6*10 = 6A + 60

Father Died and Baby was born => the Total number of people in the family is Same (6)
Baby born today so age of baby = 0

(6A +60 - x)/6 = 6A/6
=> A + 10 -(x/6) = A
=> x/6 = 10
=> x = 60

Therefore we can conclude that the father was 60 years old when he died.

let 'b' be the Length of bridge from cow to the near end of the bridge and 'a' be the distance of the train from the bridge.
'x' be speed of cow => '4x' speed of train
Then the total length of the bridge 2b + 10.
(a-2)/4x = b/x
=> a-2 = 4b........(1)
Now if it had run in opposite direction
(a+2b+10-2)/4x = (b+10-2)/x
=> a - 2b = 24......(2)
Solving (1) and (2)
b = 11 ,
Therefore length of the bridge is 2 x 11 + 10 = 32mts.

After falling it bruises, similarly after knocking it bumps.

Hence, Bruise : Fall :: Bump : Knock.

$$\begin{gathered} ?2=400+16650x100 \\ ?= 8 \end{gathered}$$