Math, asked by shubhangibharte55, 11 hours ago

A number is less than 50. It is multiple of 7 it has 3 factors. which is that number
please give the correct answer please ​

Answers

Answered by RvChaudharY50
2

Solution :-

checking multiple of 7 less than 50 and their factors :-

  • 7 = 1 *7 = 1 and 7 = 2 factors
  • 14 = 2 * 7 = 1, 2, 7 and 14 = 4 factor
  • 21 = 3 * 7 = 1, 3, 7 and 21 = 4 factors
  • 28 = 2 * 2 * 7 = 1, 2, 4, 7, 14 and 28 = 6 factors
  • 35 = 7 * 5 = 1, 5, 7 and 35 = 4 factors
  • 42 = 2 * 3 * 7 = 1, 2, 3, 6, 7, 14, 21 and 42 = 8 factors
  • 49 = 7 * 7 = 1 , 7 and 49 = 3 factor .

therefore, required number is 49 .

Method 2) :-

Concept used to find total number of factors :-

when N is a composite number and a,b and c are its prime factors. Then :-

  • N = a^p * b^q * c^r
  • Total Number of factors = (p + 1)(q + 1)(r + 1)

checking total factors of multiple of 7

→ 7 = 1 * 7¹ = (1 + 1) = 2 factors

→ 14 = 2¹ * 7¹ = (1 + 1) * (1 + 1) = 2 * 2 = 4 factors .

→ 21 = 3¹ * 7¹ = (1 + 1) * (1 + 1) = 2 * 2 = 4 factors .

→ 28 = 2² * 7 = (2 + 1) * (1 + 1) = 3 * 2 = 6 factors .

→ 35 = 5¹ * 7¹ = (1 + 1) * (1 + 1) = 2 * 2 = 4 factors .

→ 42 = 2¹ * 3¹ * 7¹ = (1 + 1) * (1 + 1) * (1 + 1) = 2 * 2 * 2 = 8 factors .

→ 49 = 7² = (2 + 1) = 3 factors .

Hence, required number is 49 .

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Answered by amitnrw
2

Given : A number is less than 50. It is multiple of 7 it has 3 factors

To Find : the number

Solution:

Only perfect Square numbers have odd number of factors

all other number have even number of factor

As its given that

Number has 3 factors and 3 is odd hence  number must be a square

As number is multiple of 7

and 7 is prime

Hence number must have square of 7

Hence 7² = 49  

49 is less than 50

and factors are  1 , 7  and 49  which are 3

Hence required number is  49

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