To find the number of pages in the book, we need to find the least common multiple (LCM) of the numbers 2, 5, and 7. The LCM is the smallest multiple that is divisible by all three numbers.
LCM(2, 5, 7) = LCM(LCM(2, 5), 7) = LCM(10, 7)
Now, let's find the LCM of 10 and 7. We can use the following formula to find the LCM:
LCM(a, b) = (a * b) / GCD(a, b)
Here, GCD represents the greatest common divisor.
GCD(10, 7) = 1 (since 10 and 7 are relatively prime)
Now, we can find the LCM:
LCM(10, 7) = (10 * 7) / 1 = 70
So, the book has 70 pages.