DI & MENTAL DI & MENTAL ABILITYABILITY

An aeroplane flies from city X to Y @ 500 km. per hour, and returns back

from Y to X @ 700 km per hour. What is the average speed of the aeroplane?

• Step 1. take harmonic mean of these twofigures: 500 & 700.

• Step 2: add: 1/500 +1/700• = 1200 / 350000• Step 3: multiply ½ by 1200/350000• = 6/3500• Reverse it: 3500/ 6 = 583 approx. ans.

Following chart shows no. of students appeared in CAT = total no of students were 104477. 64000 students were

able to get admission on the basis of the test. Out of these students 25% were repeaters and remaining were

freshers. What % of repeaters were able to take admission?

Repeaters

freshers

Answer:• By observation, it is clear that the

angle of pie chart for repeaters isabout 75-80. No. of repeaters mustbe close to (78/360*104477) =22000 approx. out of 64000, 16000are repeaters. This is (16/22*100) is72% Ans. (approx.).

Data sufficiency: Is A a male or female?

1. A has equal number of brother andsisters

2 One of the sibling of A (of opposite sex) has equal number of brothers and sisters.

Answer:• Cant be determined .

How many days do 4 men and 6 children take to

complete a work?• 6 men and 16 women complete the

work in 12 days• 24 women and 8 children complete

the work in 8 days.

Anwer: • Cannot be determined with the given

information.

Data sufficiency: what is relation between X

and Y?• X is a doctor, and Y is one of the

parents of X.• Y has two children – one son and one

daughter.

Answer :• Cannot be determined.

These are the data regarding admission in a college

1200600300Total

500Girls

700100Boys

TotalComm

erceScien

ceArts

What is the number of boys taking commerce, if it is given that the ratio of boys in arts and commerce is 1:2?

• There are total 600 students in artsand commerce. So in commerce, wehave 400 students (2/3 *600).

What is the median among the following: 2,77, 43,12,108,32,90?

• Step 1: put them in ascending order. • Step 2: find forth number (7+1 / 2 =

4). • Ans : 43.

What is the average speed of a rider, who rides four equal distances at the speed of

20,30,40,50 respectively?

• Step 1: calculate harmonic average ofthese

• Step 2: 1/20 +1/30 +1/40+1/50 =77/600

• Step 3: multiply it by ¼ : 77 / 2400• Step 4: reverse it: 31.16 Ans.

These are energy transmission costs from one city to another. We want to minimise

transmission costs. We shall transmit energy only between cities with costs less than 400.

how many options do we have?

4005006007891200F

380500578567800E

457456456430D

800600357300C

900450700400200B

700400260250200A

FEDCBA

Answer:• We have only 7 options.

In the last exercise, we want to transmit energy to E – which are

the best 4 options in order?• The hierarchy is (least cost first) :

A,F (equal), B,C. ans.• A and F have costs of 400 only.• B has cost of 450 and c has cost of

600. So order is AFBC Ans.

There are 3 robbers. A farmer gives 1/3 of his gold coins and 4 goats to first. He gives 1/3rd of

remaining goats and 4 gold coins to II. To the III he gives 1/3rd of remaining gold coins and 4 goats. Now he has equal no. of gold coins and goats. He

had total 46 goats and gold coins in the beginning. One goat is equal to 3 gold coin. What was his

initial wealth?

• Gold coin = x. Goats = 46-x;• First step: 2/3x ; 46-x-4 (left out after I robber)• (2/3x-4)2/3 = (((46-x)-4)*2/3)-4)• 4/9x-8/3=(28-2/3x)-4• 10/9x = 24 +8/3 = = 10/9x =80/3• X=80/3 *9/10 =24 Goats = 22 Value = 66• Total wealth: 66+24 = 90 Ans.

A computer programme has following algorithm: Step 1: x=2, y=1; Step 2:x=x^2 Step 3:y=y^2+x+1; Step

4:if y>=50 stopelse go to step 2. what is the value of Y at the end.

• In first iteration, x=4,y=6; in II weget x=16, Y= 36+16+1 = 53

• Therefore answer is 53 ans.

1000 liters of milk is traded by traders. Ist trader removes 50 liters and add

that much water. II & III also does the same. What is the level of pure milk

left now?

• By alligation formulae:• 1000(1 – 50/1000)^3 =

1000*.95*.95*.95 = 857.4 lit. approx.

If AM = 55.6, Median is 52.4, What is mode?

• Formulae : mode = 3 median – 2 AM• = 3*52.4 – 2*55.6• = 157.2- 111.2= 46 ans.

What is median of the following: 12,14,16,18 ?

• Median = N+1 /2• = 4+1 / 2 = 2.5• Average of 14 & 16 is 15 Ans.

Our exports and import of X were equal. In the next 5 years, exports grew @ 10% every

year. In the same period Imports grew @2,4,10,15,20 % respectively. At the end of 5 years, which were more – exports or imports?

• Let is assume exports & imports as 100.• After 5 years, exports will be:• 100*1.1*1.1*1.1*1.1*1.1=161.05• Imports will be:• 100*1.02*1.04*1.10*1.15*1.20=161.02 (both

are almost equal; exports are slightlymore).