# Numbers- Aptitude Questions and Answers - in Hindi

 The number of prime numbers which are less then 100 is? 100 से छोटी अभाज्य संख्याओं की संख्या है A) 24 B) 25 C) 26 D) 27 Correct Answer : 25 Explanation :Prime num bers less than 100 are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97. Thus, there are 25 prime numbers less than 100 In an arithmetic progression, if 17 is the 3rd term, - 25 is the 17th term, then -1 is which term? एक समांतर श्रेणी में, यदि तीसरा पद का मान 17 है, 17 वां पद - 25 है, तो -1 कौन सा पद होगा? A) 10 B) 11 C) 9 D) 12 Correct Answer : 9 Explanation :a3 = a + 2d = 17 …(i) a17 = a + 16d = - 25 …(ii) From Eqs(i) and (ii) - 14d = 42 d = - 3 So by Eq(i), a = 23 Let, nth term of the given AP is - 1 then an = a + (n - 1)d = - 1 23 + (n - 1)(- 3) = - 1 23 - 3x + 3 = - 1 - 3n = - 1 - 26 - 3n = - 27 n = 9 Twice the first of three consecutive even integer is 6 more than the second integer. What is the third integers? तीन क्रमागत सम पूर्णांक में से पहले पूर्णांक का दोगुना , दूसरे पूर्णांक से 6 अधिक है। तीसरा पूर्णांक क्या है? A) 6 B) 8 C) 10 D) 12 Correct Answer : 12 Explanation :Let the three consecutive even integers are X, X+2, X+4 As is given, 2X = (X+2)+6 2X = X+8 X = 8 Hence, third integer = X + 4 = 8 + 4 = 12 If a, b and c are digits, then abc + bca + cab is divisible by? यदि a, b और c अंक हैं, तो abc + bca + cab किसके द्वारा विभाज्य है? A) 22 B) 37 C) 99 D) 101 Correct Answer : 37 Explanation :If a ,b ,c are digits then the numbers formed can be: abc = 100a + 10b + c bca = 100b + 10c + a cab = 100c + 10a + b The sum is abc + bca + cab= (100a + 10b + c)+(100b + 10c + a)+(100c + 10a + b) =111*a + 111*b + 111*c =111*( a + b + c) So it's divisible by 111. Factors of 111 are 1, 3, 37, 111 Therfore, number formed can be divisible by 37 (37*4 = 111) The common difference of the AP √12,√27,√48,√75 is ? समान्तर श्रेणी √12,√27,√48,√75 का सामान्य अंतर है? A) √2 B) 3 C) √3 D) √12 Correct Answer : √3 Explanation :The given AP is √12,√27,√48,√75 After simplification, it can be written as 2√3,3√3,4√3,5√3 d1= 3√3-2√3=√3 d2= 4√3-3√3=√3 So common difference is √3 There are 22 terms in an arithmetic sequence. The sum of the first and last terms is 94. If the 11th term is 45, then the 12th term is ? एक अंकगणितीय अनुक्रम में 22 पद हैं। प्रथम और अंतिम पदो का योग 94 है। यदि 11 वां पद 45 है, तो 12 वां पद है? A) 48 B) 49 C) 50 D) 51 Correct Answer : 49 Explanation :tn = a + (n – 1)d where tn = nth term, a= the first term , d= common difference As given, a + (a + 21 d) = 94 2a + 21 d = 94 ------eq1 11th term, a + 10 d = 45 2a + 20 d = 90 ------eq2 from eq1 - eq2, d = 4 after substitute value of d in eq1, a = 5 Hence 12th term is, (a + 11 d)= 5 + 11*4 = 49 The difference between the place value of 4 and 2 in the number 833749502 is ? A) 39098 B) 39998 C) 49998 D) 30098 Correct Answer : 39998 Explanation :Place value of digit 4 in the number = 40000 Face value of digit 2 in the number = 2 Their difference = 40000 - 2 = 39998 The number of natural numbers less than 100 which have exactly 3 factors is ? A) 10 B) 4 C) 12 D) 33 Correct Answer : 4 Explanation :Numbers less than 100 that have exactly three factors are 4, 9, 25 and 49. All of these numbers are squares of prime numbers, which means that their only factors are one, themselves and their square roots. 2² = 4 = factors(1,2,4) 3² = 9 = factors(1,3,9) 5² = 25 = factors(1,5,25) 7² = 49 = factors(1,7,49) Find the sum of the first 20 terms of the series : 8, -3, 11, -6, 14, -12, 17, -24,....... ? A) -2854 B) 2854 C) -3069 D) 3069 Correct Answer : -2854 Explanation :8, -3, 11, -6, 14, -12, 17, -24,....... odd term: next value is +3 of previous one 8, (+3) 11,(+3)14,(+3) 17...-3, -6, -12, -24, -48, -96, -192, -384, -768, -1536 8, 11, 14, 17, 20, 23, 26, 29, 32, 35 total => 215 even term: next value is double of previous one -3, (-3*2) -6, (-6*2) -12, (-12*2) -24.... -3, -6, -12, -24, -48, -96, -192, -384, -768, -1536 total => -3069 total => 215 + (-3069) = -2854 Find the total number of terms in the series : -3, 1, 5, 9,............., 101 ? A) 25 B) 26 C) 27 D) 28 Correct Answer : 27 Explanation :the common diffrence is d= 4 and first term a = -3 1-(-3)=4 ,5-1 =4 , 9-5 =4 nth term of AP, tn = a+(n-1)d 101 = -3 +(n-1)4 26 = n-1 number of term, n = 27 How many numbers between 1200 to 1500 are multiple of 13? A) 21 B) 22 C) 23 D) 24 Correct Answer : 23 Explanation :The first term divisible by 13 after 1200 is 1209, the last term before 1500 divisble by 13 is 1495 Let n be the number of terms multiple by 13 between 1200 and 1500 as per Tn=A+(n-1)d 1495=1209+(n-1)*13 286= (n-1)*13 n-1 = 22 n = 23 number of terms multiple by 13, n= 23 How many 2 digit numbers are divisible by 6? A) 12 B) 13 C) 14 D) 15 Correct Answer : 15 Explanation :The first two digit number divisible by 6 is 12, and last two digit divisible by 6 is 96 Tn=a1+(n-1)d Tn = the nᵗʰ term in the sequence a1 = the first term in the sequence d = the common difference between term Let a=12 , d=6, Tn=96 Now we have 96=12+(n-1)6 84=(n-1)6 n-1=14 n=15 The geometric mean of three observations 40, 50 and X is 10, then the value of X is ? तीन संख्याओं 40, 50 और x का गुणोत्तर माध्य 10 है, तो X का मान है? A) 1/2 B) 1 C) 2 D) 3 Correct Answer : 1/2 Explanation :Geometric mean observations=40,50,x => (40*50*X)1/3 =10 => 40*50*X=(10)3 => X= 1000/(40*50) => X= 1/2 The value of product 6 1/2 * 6 1/4 * 6 1/8 * 6 1/16 * -----∞ upto infinite terms? गुणनफल 6 1/2 * 6 1/4 * 6 1/8 * 6 1/16 * -----∞ अनंत शब्दों तक का मान क्या है? A) 1 B) 6 C) 36 D) 216 Correct Answer : 6 Explanation :6 1/2 * 6 1/4 * 6 1/8 * 6 1/16 * -----∞ => 6 (1/2 + 1/4 + 1/8 + 1/16 -----∞) 1/2 + 1/4 + 1/8 + 1/16 -----∞ is geometric series [a = 1/2, r = 1/2] The sum of geometric series = a / 1-r => 1/2 / 1− 1/2 => 1/2 / 1/2 => 1 Hence , 6 (1/2 + 1/4 + 1/8 + 1/16 -----∞) => 6 (1) => 6 A person is to count 4500 currency notes. Let an denote the number of notes he counts in the nth minute. If a1 = a2 = .... = a10 = 150 and a10 , a11 ,... are in an AP with common difference – 2, then the time taken by him to count all notes is ? एक व्यक्ति को 4500 नोटों की गिनती करनी हैं। n वें मिनट में जितने नोट गिनता, मान लीजिए वह संख्या an से दर्शाई गयी है। अगर a1 = a2 = .... = a10 = 150 और a10 , a11 ,... AP में हैं, जिसका आम अंतर -2 के साथ हैं, तो सभी नोटों को गिनने के लिए उसके द्वारा लिया गया समय है? A) 24 minutes B) 34 minutes C) 125 minutes D) 135 minutes Correct Answer : 34 minutes Explanation :Suppose he takes n minutes to count 4500 notes. Number of notes he counts in the 10 minute => a1+a2+........+a10 = 150*10 =1500 (a1 = a2 = .... = a10 = 150) As is given a1+a2+........+an=4500 Hence, a11+a12+.....+an = 4500-1500 = 3000 a10 , a11 ,... are in an AP with common difference −2 then a10=150 and a11=148 Now, 3000 = Sum of n terms of an A.P.(first term=148 , difference= −2) Sum of first n terms of an AP: S =(n/2)[2a + (n- 1)d] ⇒3000 = (n/2)[2*148+(n−1)*(−2)] ⇒3000 = n(148−(n−1)) ⇒3000=n(149−n) ⇒n2−149n+3000=0 ⇒(n−125)(n−24)=0 ⇒n=125,24 n=125 is not possible because it is negative[ a125= 148+(125-1)*-2 =148 - 252 < 0 ] Hence, time taken=(10+24)=34 min. Find the sum of the given series: 3 + 9 + 27 + 81 + 243 + 729 + 2187 + 6561 दी गई श्रेणी का योग ज्ञात कीजिए: 3 + 9 + 27 + 81 + 243 + 729 + 2187 + 6561 A) 9840 B) 9855 C) 7960 D) 8892 Correct Answer : 9840 Explanation :3 + 9 + 27 + 81 + 243 + 729 + 2187 + 6561 31 + 32 + 33 + 34 + 35 + 36 + 37 + 38 a{(rn - 1)/(r - 1)}, a is first term, r is common ratio, n is number of terms a = 3, r = 3, n = 8. 3 * {(38 - 1)/(3 - 1)} 3 *(6561-1)/2 3*3280 9840 The sum of the series is 9840