Call KE as a, KI as b
To calculate the perimeter of a kite, we use the formula : 2(a+b)
The perimeter is 42cm, hence a + b = 42/2 = 21 cm
Now, we can write the ratio between a and b as 2:1 (because KE is twice as long)
So, we can calculate KI by taking the sum and divide by the total ratio parts
21 : (2 + 1 ) = 7
Recheck : KI = 7 -> KE = 14
Perimeter = (7+14) x 2 = 42, and 14 is indeed 2 x 7.