1. In a batch of 10 items, we wish to extract a sample of 3 without replacement. How many different samples can we extract?
2. Let X and Y be independent random variables. Suppose the respective expected values
are E(X) = 8 and E(Y) = 3 and the respective variances are V(X) = 9 and V(Y) = 6. Let Z be
defined as Z = 2X - 3Y +5. Based on these data, the value of E(Z) is_ and the value
of V(Z) is
3. The ratio of milk water in 55 liters of adulterated milk is 7: 4. How much water must be
added to make the mixture in a ratio of 7:6?
a) 5 liters
b) 10 liters
c) 15 liters d) None of these

1) 120

2) E (Z) = 12 and Variance of Z = 90

a) 5 liters

Step-by-step explanation:

1. We can find this by suing combinations.

Here n= 10 and r= 3 so n C r

= 10 C 3= 120

2. E(X) = 8 and E(Y) = 3

Z = 2X - 3Y +5

E(Z ) = 2 E (X) - 3(E)(Y) +5   ( applying property for mean)

       = 2(8) - 3(3)+ 5 = 16+5-9= 21-9= 12

V(X) = 9 and V(Y) = 6.

V(Z) = E(Z )²-  V(X) *V(Y)   (applying property for Variance for two variables )

        = 144- 54= 90

3. 55 liters contain adulterated milk in 7: 4.

So it contains 4/ 11*55= 20 liters of water

But we want to make it a ratio of 7:6

the water will be 6/13 *55= 25.38 when rounded gives 25 liters of water

So 25- 20 = 5 liters must be added to make it a ratio of 7:6

answer: i think it's a

step-by-step explanation:

7. d. 64

8. i. 32

9. c. 125

10. j. none of the above

11. d. 81

12. i. 216

13. e. none of the above

14. g. 240

15. e. none of the above

16. g. 32

17.   e. none of the above