Quantitative Aptitude - Arithmetic Ability Questions

From statement (A),

20b = (1/2) × b × h

h = 40 cm.

Required number of signals = 5P1 + 5P2 + 5P3 + 5P4 + 5P5

= 5 + 20 + 60 + 120 + 120 = 325

S = { HHH, HHT, HTH, HTT, THH, THT, TTH, TTT }

=> n(S) = 8

E = { HHH, HHT, HTH, THH }

=> n(E) = 4

P(E) = 4/8 = 1/2

If earlier he is getting Rs. 1  per hr and working for 1 hr, income = Rs. 1
Now he is getting Rs 1.3333 per hr and working for 0.66667 hrs

Then income for 0.66667 hrs = Rs. 0.8889.

If payment per hr is increased by 33.33 %  and working hours dereased by 33.33%, then 11.11 % decrease in income.

 Since 8 does not occur in 1000, we have to count the number of times 8 occurs when we list the integers from 1 to 999. Any number between 1 and 999 is of the form xyz, where 0≤x,y,z≤9.

Let us first count the numbers in which 8 occurs exactly once.

Since 8 can occur atone place in 3C1ways. There are 3 x 9 x 9 such numbers.

Next, 8 can occur in exactly two places in 3C2×9 such numbers. Lastly, 8 can occur in all three digits in one number only.

Hence, the number of times 8 occur is 

 1×3×92+2×3×9+3×1 = 300

Total number of chairs = (3 + 5 + 4) = 12.

Let S be the sample space.

Then, n(s)= Number of ways of picking 2 chairs out of 12

= 12×11/2×1 = 66

Let n(E) = number of events of selecting 2 chairs for selecting no white chairs.

=> 8C2 = 8×7/2×1 = 28

Therefore required probability = 28/66 = 14/33.