Math Problem Statement
Find the number of positive integers between 1 to 500 that are divisible by
(ii) 2,3,5 but not by 7
Solution
We want to find how many integers between 1 and 500 are divisible by 2, 3, and 5 but not by 7.
Step 1: Least Common Multiple (LCM)
First, let's determine the least common multiple (LCM) of 2, 3, and 5.
So, we are looking for numbers divisible by 30, but not divisible by 7.
Step 2: Count numbers divisible by 30
The total number of integers divisible by 30 between 1 and 500 can be found by dividing 500 by 30:
So, there are 16 integers divisible by 30 between 1 and 500.
Step 3: Exclude numbers divisible by both 30 and 7
Now, let's find how many of those 16 numbers are divisible by both 30 and 7. To do this, we calculate the LCM of 30 and 7:
Next, we find how many numbers between 1 and 500 are divisible by 210:
So, there are 2 numbers divisible by both 30 and 7.
Step 4: Final count
To get the number of integers divisible by 30 but not divisible by 7, we subtract the 2 numbers divisible by 210 from the 16 numbers divisible by 30:
Thus, there are 14 positive integers between 1 and 500 that are divisible by 2, 3, and 5 but not by 7.
Would you like further details or have any questions?
Here are 5 related questions for further practice:
- How many integers between 1 and 1000 are divisible by 3, 4, and 6 but not by 5?
- Find the number of integers divisible by 2 and 3 but not by 5 between 1 and 300.
- How many integers between 1 and 500 are divisible by both 6 and 10?
- Find how many numbers between 1 and 1000 are divisible by 4 but not by 9.
- How many integers between 1 and 500 are divisible by 3, 5, and 7?
Tip: When working with multiple divisors, using the least common multiple (LCM) helps efficiently count divisible numbers!
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Math Problem Analysis
Mathematical Concepts
Divisibility
Least Common Multiple (LCM)
Inclusion-Exclusion Principle
Formulas
LCM(2, 3, 5) = 30
LCM(30, 7) = 210
Count of numbers divisible by x between 1 and n: floor(n / x)
Theorems
Inclusion-Exclusion Principle
Suitable Grade Level
Grades 8-10
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