2
Q:

What is the sum of all 3 digits number that can be formed using digits 0,1,2,3,4,5 with no repitition ?

A) 28450 B) 26340
C) 32640 D) 36450

Answer:   C) 32640



Explanation:

We know that zero can't be in hundreds place. But let's assume that our number could start with zero.

 

The formula to find sum of all numbers in a permutation is

 

111 x no of ways numbers can be formed for a number at given position x sum of all given digits

 

No of 1 s depends on number of digits

 

So,the answer us

 

111 x 20 x (0+1+2+3+4+5) = 33300

 

We got 20 as follows. If we have 0 in units place we can form a number in 4*5 ways. This is for all numbers. So we have substituted 20 in formula.

 

Now, this is not the final answer because we have included 0 in hundreds place. so we have to remove the sum of all numbers that starts with 0.

 

This is nothing but the sum of all 2 digits numbers formed by 1 2 3 4 5. Because 0 at first place makes it a 2 digit number.

 

So the sum for this is 11 x 4 x (1+2+3+4+5).
=660

 

Hope u understood why we use 4. Each number can be formed in 4x1 ways

 

So, the final answer is 33300-660 = 32640

Subject: Permutations and Combinations
Exam Prep: GATE , CAT , Bank Exams , AIEEE
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Q:

If each of the vowels in the word 'MEAT' is kept unchanged and each of the consonants is replaced by the previous letter in the English alphabet, how many four-lettered meaningful words can be formed with the new letters, using each letter only once in each word?

A) 3 B) 4
C) 1 D) 2
 
Answer & Explanation Answer: A) 3

Explanation:
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18 1232
Q:

In a bag containing red, green and pink tokens, the ratio of red to green tokens was 5 : 12 while the ratio of pink to red tokens was 7 : 15. What was the ratio of green to pink tokens?

A) 25 : 28 B) 36 : 7
C) 8 :25 D) 12 : 7
 
Answer & Explanation Answer: B) 36 : 7

Explanation:
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7 960
Q:

The ratio of the members of blue to red balls in abag is constant. When there were 44 red balls, the number of blue balls was 36. If the number of blue balls is 54, how many red balls will be in the bag?

A) 68 B) 32
C) 64 D) 66
 
Answer & Explanation Answer: D) 66

Explanation:
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25 2170
Q:

If each vowel of the word NICELY is changed to the next letter in the English alphabetical series and each consonant is changed to the previous letter in the English alphabetical series and then the alphabets are arranged in alphabetical order, which of the following will be fourth from the left?

A) M B) J
C) B D) O
 
Answer & Explanation Answer:

Explanation:

Thus after arranging the letters as per English alphabetical series; we get; Thus 4th letter from the left end will be K.

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16 2157
Q:

How many such pair of letters are there in the word ‘TROUBLED’ which have as many letters between them in the word as they have between them in the English alphabet?

A) 2 B) 3
C) 4 D) 5
 
Answer & Explanation Answer: A) 2

Explanation:

Hence there are two pairs

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13 1736
Q:

If it is possible to make a meaningful word with the first, the seventh, the ninth and the tenth letters of the word RECREATIONAL, using each letter only once, which of the following will be the third letter of the word? If more than one such word can be formed, give ‘X’ as the answer. If no such word can be formed, give ‘Z’ as the answer.

A) T B) X
C) N D) R
 
Answer & Explanation Answer: D) R

Explanation:

The first, the seventh, the ninth and the tenth letters of the word RECREATIONAL are R, T, O and N respectively. Meaningful word from these letters is only TORN. The third letter of the word is ‘R’.

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6 1568
Q:

16 persons are participated in a party. In how many differentways can they host the seat in a circular table, if the 2particular persons are to be seated on either side of the host?

A) 16! × 2 B) 14! × 2
C) 18! × 2 D) 14!
 
Answer & Explanation Answer: B) 14! × 2

Explanation:

(16 – 2)! × 2 = 14! × 2

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3 2310
Q:

From a pack of 52 cards, 3 cards are drawn together atrandom, What is the probability of both the cards are king?

A) 1/5225 B) 1/5525
C) 5525 D) 1/525
 
Answer & Explanation Answer: B) 1/5525

Explanation:

n(S) = 52C3 = 132600/6 = 22100

n(E) = 4C3 = 24/6 = 4

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8 1612