h = 9.2 cm
Solution:
Base of smaller triangle = 5 cm
Height of smaller triangle = 2.3 cm
Base of larger triangle = 15 cm + 5 cm = 20 cm
Height of larger triangle = h
[tex]$\frac{2.3}{5}=\frac{h}{15+5}[/tex]
[tex]$\frac{2.3}{5}=\frac{h}{20}[/tex]
Multiply by 20 on both sides.
[tex]$20 \times \frac{2.3}{5}=\frac{h}{20} \times 20[/tex]
[tex]$\frac{46}{5}=h[/tex]
9.2 = h
So that Ryan should have add 15 and 5 to get a denominator of 20 on the right sides of the first line. Doing so gives the correct value, h = 9.2 cm.
