Answer:
7
Explanation:
Given,
△ABC ~ △DEF
( ~ means similar )
To find : missing side length
Similar triangle rule : -
If two triangles are similar, their corresponding sides are similar.
So,
AB ~ DE
BC ~ EF
AC ~ DF
Let the missing side length ( DF ) be " x ".
Note : -
When the corresponding sides are divided, their ratios will be same.
That is,
AB / DE
= 20 / 4
= 5 / 1
= 5 : 1
BC / EF
= 40 / 8
= 5 / 1
= 5 : 1
AC / DF should also be equal to 5 : 1.
AC / DF = 5 : 1
35 / x = 5 / 1
Cross multiply,
x * 5 = 35 * 1
5x = 35
Divide 5 on both sides,
x = 35 / 5
x = 7
Therefore,
the missing side length is 7.