Question

Keith's height and his nephews height was at a ratio of 15:7 then, keith's Height increased by 16% and his nephews height doubled. If Keith is now 34cm taller than his nephew, what is their total current height?

Answer 1

Answer:

311.6 cm

Step-by-step explanation:

To solve this problem, let's call:

k = Keith's height

n = nephew's height

Since the ratio is 15:7, we have

$\frac{k}{n}=\frac{15}{7}\\k=\frac{15}{7}n$ (1)

Then, Keith's height is increased by 16%, so the new height of Keith is

$k'=k+0.16 = 1.16k$  (2)

While the nephew's height is doubled:

$n'=2n$ (3)

We also know that Keith is now 34 cm taller than his nephew, so

$k'=n'+34$ (4)

Substituting (2) and (3) into (4), we get

$1.16k=2n+34$

And substituting (1),

$1.16\cdot \frac{15}{7}n=2n+34$

Solving for n,

$2.49n=2n+34\\\\0.49n=34\\n=\frac{34}{0.49}=69.4$

So the current height of the nephew is:

$n'=2n=2(69.4)=138.8 cm$

While Keith's current height is

$k'=138.8+34=172.8 cm$

So their total current height is

$k'+n'=172.8+138.8=311.6 cm$