Question

The measures of two sides of a triangle are 7.3 centimeters and 2.94 centimeters. The triangle's perimeter is 14.8 centimeters. Which equation could not be used to find the length of the third side?
7.3 + 2.94 + x = 14.8
14.8 = x + 10.24
14.8 - x = 7.3 + 2.94
x - 14.8 = 2.94 + 7.3

Answer 1

The perimeter is the sum of all lengths of the side of a polygon. For a triangle it is expressed as:

P = a + b + c

We let a = 7.3, b = 2.94 and c=x

Therefore, the perimeter of the given triangle is:

14.8 = 7.3 + 2.94 + x

From the options given, the correct answer is the last option. The expression, x - 14.8 = 2.94 + 7.3, will give an erroneous value of the third side. It will be more than the perimeter given.