20. ABCDE are sisters. Each of them gives 4 gifts and each receives 4 gifts No two sisters give the same combination ( e.g. if A gives 4 gifts to B then no other sisters can give four to other one.)
(i) B gives four to A.
(ii) C gives 3 to E.
How much did A,B,C,E give to D?

Donor no of gifts A 1 B - C 1 D 2

21.

There are some bulbs,which are numbered from 1 to 100.all the bulbs are in on conditions. The following operations are performed:-
1. Those bulbs number which are divisible by 2 are switched OFF.
2. Those bulbs numbered which are divisible by 3 are switched ON (which are already OFF) and OFF bulbs are switched ON.
3. Similarly bulbs numbers divisible by 4 are either switched ON or OFF depending upon there previous condition.
4. This procedure is adopted till 100th bulb.
At the end there were how many bulbs which were in ON condition?
Ans:

10

22. There are different numbers related with A,B,C,D,E.such that, AB*CD=EEE. E*CD-AB=CC.
Find AB*D.

 BE

23. Find the total no of 10 digits whose sum is 4

1111000000 ,1010101000,…

24. A, B, C are 3 girls and there are 770 Apples. For every 4 Apples, A takes,B takes 3. For ever 6 Apples, C takes 7 Apples?

261:145:303.