Saima goes to her friend every twenty days and laiba goes to same friend every twenty five days. After how many days saima and laiba will visit the friend together?
Answers
Answer: 100 days
Step-by-step explanation:
Since we have to find when the numbers 20 and 25 meet, we will have to find the LCM of 20 and 25.
To find LCM:
If you do not know the prime factorization method:
In the first step we divide 20 and 25 by 5
20 ÷ 5 = 4
25 ÷ 5 = 5
In the second step we only divide 5 by 5, as 5 is not a factor of 4 but it is a factor of 5.
5 ÷ 5 = 1
In the third step we only divide 4 by 2, as 1 can no longer be divided.
4 ÷ 2 = 2
In the last step we divide only 2 by 2, as 1 can no longer be divided.
2 ÷ 2 = 1
Since now, both the number are no longer divisible, we stop.
To find the LCM, we need to multiply all the prime factors.
∴ The LCM of 20 and 25 = 5 x 5 x 2 x 2
= 100
∴ Saima and Laiba will visit the friend together after a 100 days.
Note: Only prime numbers can be used to divide the numbers in this method.
The attachment below shows how to present the prime factorization:
