Triangle Area Calculation: Finding ADC Area with Given Segments (15cm, 13cm, 5cm)

Question

The perimeter of the triangle ABD shown below is 36 cm.

Given in cm:

AB = 15

AC = 13

DC = 5

CB = 4

Calculate the area of triangle ADC.

151515131313AAABBBDDDCCC54

Video Solution

Solution Steps

00:00 Calculate the area of triangle ADC
00:02 Side DB equals the sum of its parts (DC+CB)
00:10 Let's substitute appropriate values
00:14 Let's calculate and find the length of side DB
00:20 The perimeter of triangle ABD equals the sum of its sides
00:32 Let's substitute appropriate values
00:40 Let's calculate and solve to find the height (AD)
00:45 Let's isolate AD
00:56 And this is the height value (AD)
01:06 Let's use the formula for calculating triangle area
01:09 (height(AD) multiplied by base(DC)) divided by 2
01:14 Let's substitute appropriate values
01:18 Let's calculate and solve
01:23 And this is the solution to the problem

Step-by-Step Solution

Using the given data of the triangle's perimeter we will first find the side AD by calculating the sum of all the sides of the triangle:

AD+9+15=36 AD+9+15=36

AD+24=36 AD+24=36

AD=3624=12 AD=36-24=12

Now that we know that AD is equal to 12, we are able to deduce that AD is also the height from BD since it forms a 90-degree angle.

If AD is the height from BD, it is also the height from DC.

Now we can calculate the area of the triangle ADC:

AD×DC2 \frac{AD\times DC}{2}

12×52=602=30 \frac{12\times5}{2}=\frac{60}{2}=30

Answer

30 cm²