Solution:

47 + 53 + 59 + 61 = 220

Solution:

two hours.

Harish who could paint the wall in 3 hours could paint 2/3 of the wall in just two hours. Ganpat who paint the wall in 6 hours could paint 1/3 of the wall in two hours.
2/3 + 1/3 = 1.

Solution:

100/9 (fraction number is also a number)

lets say 'X' is the number.
10/X = X - 10
9X = 100
X = 100/9

Solution:

Lady:135 , Baby:25 & Dog:10

Solution:

The required number is 236 and the sum is 11.

It is given that the first two digits of the required number are prime numbers i.e. 2, 3, 5 or 7. Note that 1 is neither prime nor composite. Also, the third digit is the multiplication of the first two digits. Thus, first two digits must be either 2 or 3 i.e.
22, 23, 32 or 33 which means that there are four possible numbers - 224, 236,326 and 339.
Now, it is also given that - the difference between it's reverse and itself is 396.
Only 236 satisfies this condition. Hence, the sum of the three digits is 11.

Solution:

100. Looks hard? Don't worry, just work it backwards and you'll find it very easy.

Solution:

44 and 66

Solution:

Sadaf had 50pound and Tanu had 30 pound.

Sadaf Tanu
50 30
20 60
40 40
0 80

Solution:

Just 1

Solution:

As noted, all three are 140 years old. Thus, a+b+c=140, where a is grandfather, b is son, and c is grandson. Additionally, grandson being about as many days old as son is in weeks gives 365c=52b. Finally, the grandson being as many months as I am in years gives 12c=a. Thus, the following are known.

a+b+c=140
365c=52b or b=365c/52
12c=a

By calculation and substitution we have as follows.

12c + 365c/52 +c = 140
624c + 365c + 52c = 7280
1041c = 7280
c = 6.99, or 7 (teaser said 'about')
so, as 12c = a, then a = 84.

I am 84 years old.
As an aside, my son is 49