Which are the Most Important 3i Infotech Interview Questions? Here is a list of question with solution you can go through to clear 3i infotech interview. Visit for more such questions.

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Question 1. Twice The Speed Of A Boat Downstream Is Equal To Thrice The Speed Upstream. The Ratio Of Its Speed In Still Water To The Speed Of Current Is
Answer :
Let the boat speed in still water be b.
Let the stream speed be x.
2(b+ x) = 3(b-x)

Question 2. A Person Has A Chemical Of Rs. 25 Per Litre. In What Ratio Should Water Be Mixed With That Chemical So That After Selling The Mixture At Rs. 20/litre He May Get A Profit Of 25% ?
Answer :
This can be solved using alligation.
What is required at the end of mixing is a price of 20/1.25 = 16.
So the alligation would look like this –
Water/0 Mixture/16 Chemical/25
Hence the ratio would be (25 – 16) : 16 = 9 : 16
Hence required ratio of Water : Chemical is 9:16.

Question 3. The Difference Between The Simple Interest And Compound Interest On A Certain Sum Of Money For 2 Years At 15% P. A. Is Rs. 45. Find The Sum ?
Answer :
Since we know that the interest rate is 0.15, and knowing that the difference between two years of compound interest is nothing but interest on interest, we can find the first year’s interest as –
45/0.15 = 300.
Now if the interest is 300 at the end of one year, then the principal is 300 / 0.15 = 2,000

Question 4. How Many Terms Are There In An A.p. Whose First And Fifth Terms Are -14 And 2, Respectively, And The Sum Of Terms Is 40 ?
Answer :
Now the common difference of this AP is 16/4 = 4.
The sum of an AP is n/2 {2a + (n – 1)d}
Substituting we get, 40 = n/2 {2×-14 + (n – 1)4}
The best way to solve this is by plugging options. Put in n = 10 and get the RHS as 40.

Question 5. In A Class, 50 Students Play Cricket, 20 Students Play Football And 10 Play Both Cricket And Football. How Many Play At Least One Of These Two Games ?
Answer :
The required answer is 50 + 20 – 10 = 60.

Question 6. A Bottle Is Full Of Dettol. One-third Of It Is Taken Out And Then An Equal Amount Of Water Is Poured Into The Bottle To Fill It. This Operation Is Done Four Times. Find The Final Ratio Of Dettol And Water In The Bottle ?
Answer :
As in denominator we have to take 1/3 four times so, we start by assuming 81 ml of dettol in the bottle. After the first iteration you will be left with
2/3 × 81 = 54 ml. After the second iteration you will be left with
2/3 × 54 = 36 ml. After the third iteration you will be left with
2/3 × 36 = 24 ml. After the fourth iteration you will be left with
2/3 × 24 = 16 ml. So the required ratio will be 16 : (81 – 16) = 16 : 65

Question 7. In A Survey Of Defaulted Payments Of Electrical Bills Of A Residential Complex Of 125 Houses, It Is Found That 50 Houses Defaulted On Their Payment Of Electrical Bills In January, 60 In February And 40 In March. Houses Can Default In Consecutive Months Only. 20 Defaulted In January And February. 10 Defaulted In February And March. How Many Houses Defaulted In All The 3 Months?
Answer :
We use formula for intersection of three sets, keeping in mind that Jan ∩ Mar does not exist, since they are not consecutive months.
Let x be the number of people defaulting in all 3 months.
We get the equation as : 125 = 50 + 60 + 40 – 20 – 10 + x. Solving we get x = 5.

Question 8. India Plays Two Matches Each With West Indies And Australia. In Any Match The Probabilities Of India Getting Points 0, 1, 2 Are 0.45, 0.05 And 0.50 Respectively. Assuming That Outcomes Are Independent, The Probability Of India Getting At Least 7 Points Is
Answer :
Getting 7 points is possible in 2 cases.
Case 1: India wins all 4 matches.
Probability: (.5)4 = .0625.
Case 2: India wins any of the 3 matches and draws the remaining match. This can happen in total 4 ways. Probability: 4 x (.50)3 x (.05) = .025.
So, required probability: .0625 + .025 = .0875

Question 9. In Order To Obtain An Income Of Rs. 650 From 10% Stock At Rs. 96, One Must Make An Investment Of
Answer :
To obtain Rs. 10, investment = Rs. 96.
To obtain Rs. 650, investment = Rs.96/10x 650 = Rs. 6240.

Question 10. Express A Speed Of 36 Kmph In Meters Per Second ?
Answer :
36 * 5/18 = 10 mps

Question 11. Express 25 Mps In Kmph?
Answer :
25 * 18/5 = 90 kmph

Question 12. A Boy Has Nine Trousers And 12 Shirts. In How Many Different Ways Can He Select A Trouser And A Shirt?
Answer :
The boy can select one trouser in nine ways.
The boy can select one shirt in 12 ways.
The number of ways in which he can select one trouser and one shirt is 9 * 12 = 108 ways.

Question 13. How Many Three Letter Words Are Formed Using The Letters Of The Word Time ?
Answer :
The number of letters in the given word is four.
The number of three letter words that can be formed using these four letters is ⁴P₃ = 4 * 3 * 2 = 24.

Question 14. Using All The Letters Of The Word “thursday”, How Many Different Words Can Be Formed ?
Answer :
Total number of letters = 8
Using these letters the number of 8 letters words formed is ⁸P₈ = 8!.

Question 15. Using All The Letters Of The Word “nokia”, How Many Words Can Be Formed, Which Begin With N And End With A ?
Answer :
There are five letters in the given word.
Consider 5 blanks .
The first blank and last blank must be filled with N and A all the remaining three blanks can be filled with the remaining 3 letters in 3! ways.
The number of words = 3! = 6.

Question 16. The Number Of Arrangements That Can Be Made With The Letters Of The Word Meadows So That The Vowels Occupy The Even Places ?
Answer :
The word MEADOWS has 7 letters of which 3 are vowels.
As the vowels have to occupy even places, they can be arranged in the 3 even places in 3! i.e., 6 ways. While the consonants can be arranged among themselves in the remaining 4 places in 4! i.e., 24 ways.
Hence the total ways are 24 * 6 = 144.

Question 17. The Number Of Permutations Of The Letters Of The Word ‘mesmerise’ Is_.
Answer :
n items of which p are alike of one kind, q alike of the other, r alike of another kind and the remaining are distinct can be arranged in a row in n!/p!q!r! ways.
The letter pattern ‘MESMERISE’ consists of 10 letters of which there are 2M’s, 3E’s, 2S’s and 1I and 1R.
Number of arrangements = 9!/(2!)2 3!

Question 18. A Committee Has 5 Men And 6 Women. What Are The Number Of Ways Of Selecting 2 Men And 3 Women From The Given Committee ?
Answer :
The number of ways to select two men and three women = ⁵C₂ * ⁶C₃
= (5 *4 )/(2 * 1) * (6 * 5 * 4)/(3 * 2)
= 200

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