Solution:

Sadaf had 50pound and Tanu had 30 pound.

Sadaf Tanu
50 30
20 60
40 40
0 80

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

Solution:

The digits are 12, 5, 6, and 8

Solution:

20 times

8,18,28,38,48,58,68,78,98,80,81,82,83,84,85,86,87,88,88(2),89

Solution:

Charley Smallish and his best girl could trolley three times as fast as they could walk. Therefore, three-quarters of their outing time was spent in walking, and but one-quarter in riding, since they had to walk back.

They rode for two hours, going 18 miles, and walked back in six hours, thus consuming their eight hours.

Solution:

Starting with 1 marble in a bag, each bag contains double the number of marbles as the previous bag.
ie 1,2,4,8,16,32,64,128,256,512.

That way whatever number of marbles I would ask for you would just add up the boxes to equal the number asked.

Solution:

The complete addition looks as follows:

  167161 +
  664711 +
  162166 +
  164611
-------------
1158649

Solution:

9376

Looking at the last digit, the last digit must be either 0, 1, 5 or 6.
Then looking at the last two digits, the last two digits must be either 00, 01, 25 or 76.
Then looking at the last three digits, the last three digits must be either 000, 001, 625 or 376.
Then looking at the last four digits, the last four digits must be either 0000, 0001, 0625 or 9376.
Out of those, only 9376 is a 4 digit number

Solution:

143547

Solution:

2519

The number has to end in 9.
Looked brute force for small numbers.
59 and 119 were promising, but no cigar.

Then looked for agreement among
39 + multiples of 40,
69 + multiples of 70 and
89 + multiples of 90
Smallest one was 2519.