Find the part of the given sentence that has an error

The HCF of 450 and 740 is 150, their LCM is:

The LCM of two natural numbers is 8 times their HCF. If the product of given two numbers is 7,200, then find the LCM of the numbers.

LCM and HCF of two numbers are respectively 3 and 18. If one of them is 9, find the other number.

The HCF of two numbers is 21. Which of the following can never be their LCM?

Three numbers a, b and c are co-prime to each other such that ab = 99 and bc = 275. Find the value of (a + b + c).

How many pairs of natural numbers (x, y) exist such that x>y and the product of x, y and HCF (x, y) = 2520? solve this 

Find the LCM of the following fractions:

4/13, 5/7 and 7/5 

Find the total number of Prime factor in the given expression?

3¹⁵ × 5⁶ × 6⁸

Two numbers are in the ratio 4 : 5 and their least common multiple (LCM) is 1800. What are the two numbers?

What is the difference between the LCM and HCF of 36, 40?