7 orange trees, 28 apples trees and 42 mangoes trees have to be planned in rows such that each row contains the same number of trees of one variety only. Minimum number of row in which the trees may be planted is:

Correct option is D

Given:

7 orange trees, 28 apple trees, 42 mango trees

Solution:

Calculate the HCF 

HCF of 7, 28, and 42 = 7 

This means each row will contain 7 trees.

​Calculate the Number of Rows ;

For orange trees: $$\frac{7}{7}$$ = 1 row

​For apple trees: $$\frac{28}{7}$$ = 4 row

​For mango trees: $$\frac{42}{7}$$ = 6 row

​Total Number of Rows: 

1 + 4 + 6 =11 rows 

The minimum number of rows required is 11 

Thus, correct answer is (d) 11