Last year, Katie earned £16200 - OCR - GCSE Maths - Question 16 - 2017 - Paper 1

Using a calculator or by using greatest common divisor methods, we can find:

After simplification, we find that:

$\frac{6400}{16200} \approx \frac{32}{80} \Rightarrow 32 : 80$

Dividing both sides by 8 gives:

$\Rightarrow 4 : 10$

And further reducing gives us:

$\Rightarrow 2 : 5$

Katie estimated the ratio to be 3 : 8. To check if these are equivalent, we can express both ratios in decimal form:

For 3 : 8:

$\frac{3}{8} = 0.375$

For 2 : 5:

$\frac{2}{5} = 0.4$

Since 0.4 is not approximately equal to 0.375, we can conclude that Katie's estimate is incorrect.