Question

Alex is planting trees. He has enough trees to plant 3, 6, or 7 trees in each row. So, Alex can plant atleast trees.

• A. 42
• B. 36
• C. 28

Answer 1

The correct option is A 42

Alex can plant
3, 6, or 7 trees in a row.

We have to find the least number of trees Alex can plant.

To do so, we need to find lowest common multiple (LCM) of 3, 6, and 7 using the ladder method.

So, let us write all three numbers on a horizontal line and divide these numbers using a prime number, which exactly divides at least one of the given numbers.


Write the quotients in the next line.

If the number is not exactly divided, write it in the next row along with the quotient of another number.

Repeat the process until the quotients are prime numbers.


Now, to obtain the LCM, we multiply all the divisors and the quotients in the last row.

So, LCM of 3, 6, and 7 = 42

∴ Alex can plant atleast 42 trees.