model 1 Basic formula of LCM & HCF Section-Wise Topic Notes With Detailed Explanation And Example Questions
MOST IMPORTANT quantitative aptitude - 5 EXERCISES
The following question based on LCM & HCF topic of quantitative aptitude
(a) 276
(b) 299
(c) 345
(d) 322
The correct answers to the above question in:
Answer: (d)
HCF is 23. So the other two numbers would be,
(23 * 13) and (23 * 14).
Thus Larger Number = 23 * 14 = 322.
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Read more finding lcm Based Quantitative Aptitude Questions and Answers
Question : 1
LCM of two numbers is 225 and their HCF is 5. If one number is 25, the other number will be?
a) 5
b) 25
c) 45
d) 225
Answer »Answer: (c)
Given, LCM = 225, HCF = 5,
First Number = 25 , Second Number = ?
We can find the Second Number with the help of given formula,
"LCM × HCF = 1st Number× 2nd Number"
⇒ 225 × 5 = 25 × 2nd Number
2nd Number = ${\text"225 x 5"}/25$
∴ 2nd Number = 45
Question : 2
The H.C.F. of two numbers is 96 and their L.C.M. is 1296. If one of the number is 864, the other is
a) 132
b) 135
c) 140
d) 144
Answer »Answer: (d)
Using Rule 1 :
1st number × 2nd number = L.C. M. × H.C.F,
First number × Second number = HCF × LCM
⇒ 864 × Second number
= 96 × 1296 ⇒ Second number
${96 × 1296}/864$ = 144
Question : 3
The HCF and LCM of two numbers are 12 and 924 respectively. Then the number of such pairs is
a) 0
b) 1
c) 2
d) 3
Answer »Answer: (c)
Question : 4
The product of two numbers is 2160 and their HCF is 12. Number of such possible pairs is
a) 1
b) 2
c) 3
d) 4
Answer »Answer: (b)
HCF = 12
Numbers = 12x and 12y
where x and y are prime to each other.
∴ 12x × 12y = 2160
⇒ xy = $2160/{12 × 12} $
= 15 = 3 × 5, 1 × 15
Possible pairs = (36, 60) and (12, 180)
Hence , Number of such possible pairs is 2.
Question : 5
The L.C.M. of three different numbers is 120. Which of the following cannot be their H.C.F.?
a) 8
b) 12
c) 24
d) 35
Answer »Answer: (d)
We know that:
LCM is the least common multiple of the given numbers whereas HCF is the highest common factor of those numbers.
Then, LCM is the multiplication of one common factor of the numbers and the other different factors of the numbers.
Write the LCM = 120 into factored form, that is
120 = 2 × 2 × 2 × 3 × 5
= 4(2 × 3 × 5)
⇒ 4 is the common factor of the numbers.
So, the HCF of three numbers is a multiple of 4.
Multiples of 4: 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, ...
Therefore, 35 is not the multiple of 4, then 35 cannot be their HCF.
Question : 6
The HCF and LCM of two numbers are 12 and 924 respectively. Then the number of such pairs is
a) 0
b) 1
c) 2
d) 3
Answer »Answer: (c)
The HCF and LCM of two numbers are 12 and 924.
Let the numbers be 12p and 12q where p and q are prime to each other.
∴ LCM = 12pq
∴ 12pq = 924
⇒ pq = 77
∴ Possible pairs are (1 , 77) and (7 ,11)
Hence , required answer is 2.
LCM & HCF Shortcuts and Techniques with Examples
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model 1 Basic formula of LCM & HCF
Defination & Shortcuts … -
model 2 find lcm of numbers
Defination & Shortcuts … -
model 3 find hcf of numbers
Defination & Shortcuts … -
model 4 addition, subtraction, multiplication and division with lcm & hcf
Defination & Shortcuts … -
model 5 lcm & hcf vs ratios
Defination & Shortcuts …
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