In a question paper, there are four multiple choice type question. Each question has five choices with only one choice for its correct answer. What is the total number of ways in which a candidate will not get all the four answers correct?

Given, P = ? 9375, R₁ = 2% and R₂ = 4%
According to the formula,
A = P (1 + R₁/100) (1 + R₂/100)
= 9375 (1 + 2/100) (1 + 4/100)
= 9375 x (51/50) x (26/25)
= 7.5 x 51 x 26
= ? 9945

Now CI = A - P = 9945 - 9375 = ? 570

? Gain = (S.P. of 100 bananas) - (C.P. of 100 bananas)
? (S.P.of 20) = (S.P of 100) - (C.P. of 100)
? S.P.of 80 = C.P. of 100

Let C.P. of each banana = Re. 1
C.P. of 80 banana = Rs. 80
S.P. of 80 banana = Rs. 100

? Gain % = (20 / 80) x 100 % = 25%

Average of first n natural numbers = ( n + 1 ) / 2
= ( 79 + 1 ) / 2
= 40

Then, their L.C.M. = 6x.

So, 6x = 48 or x = 8.

∴ The numbers are 16 and 24.

Hence, required sum = (16 + 24) = 40.

Let us assume the first part is A then second part will be 50 - A.
According to question,
Sum of their reciprocals is 1/2.
1/A + 1/(50 - A) = 1/12
? (50 - A + A)/(50 - A)A = 1/12
? (50)/(50 - A)A = 1/12
? (50) x 12 = 1 x (50 - A)A
? 600 = (50 - A)A
? 600 = 50A - A²
? A² - 50A + 600 = 0
? A² - 30A - 20A + 600 = 0
? A(A - 30) - 20(A - 30) = 0
? (A - 30)(A - 20) = 0
? (A - 30) = 0 or (A - 20) = 0
? A = 20 , 30

Total time taken = (3/10 + 3/20 + 3/30 + 3/60) hrs.
= 3/5 hrs.

? Average speed = {12 / (3 / 5)} km/hr.
= (12 x 5 ) / 3 km/hr.
= 20 km/hr.

Given Exp. = 3.57 - 2.14
= 3 + (57 / 99) - 2 - (14 / 99)
= 1 + (57 / 99) - (14 /99)
= 1 + 43/99
= 1.43