Quantitative Aptitude - Arithmetic Ability Questions

Given speed of jogger = 9 kmph
Speed of train = 45 kmph
As they are in same direction,
Relative speed = 45 - 9 = 36 kmph = 36x5/18 = 10 m/s
Distance = 240 + 120 = 360 mts
Time = distance/speed = 360/10 = 36 sec.

 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

Let no. of boys be 'B' and no. of girls be 'G'

Here from given data,

B + G = 1650 .....(1)

B - G = 400 .....(2)

From (1) & (2), we get

2B = 2050

=> B = 1025

=> G = 1650 - 1025 = 625

Hence, the % of girls = 625 x 100/1650

=> 38% (approx).

1 boy's 1 day work = 1/70

1 girl's 1 day work = 1/140

(5 boys + 10 girls)'s 1 day work = (5/70 + 10/140) = (1/14 + 1/14) = 1/7

5 boys and 10 girls will complete the work in 7 days.

Sum ⇒ Amount 

A = (SI x TD)/(SI - TD)

Given the salaries are in the ratio of 4 : 5 : 6

Now the salaries are increased by 50%, 60% and 50% respectively

The New ratio of salaries will be

4 x (150/100) : 5 x (160/100) : 6 x (150/100)

= 6 : 8 : 9

The new ratio of salaries of Akhil, Arun and Karthik is 9 : 8 : 6

Probability of atleast one failure
= 1 - no failure > 31/32
= 1 - P5 > 31/32
=  P5<1/32
= p < 1/2
Also p > 0
Hence p lies in [0,1/2].