Verified Answer :

One Way:
We can change the mixed number to a decimal for comparing.

\(1\frac{1}{4}\) m = \(\frac{5}{4}\) m = 1.25 m

1.4 m     >    1.25 m
Darren   >     Luke

Darren's jump was higher by (1.4-1.25) 0.15 m

Or another way change the decimal to a fraction and the mixed to an improper fraction too.

\(1\frac{1}{4}\) = \(\frac{5}{4}\) (Luke)
1.4 = \(\frac{7}{5}\)                               (Darren)
We need a common denominator to compare
\(\frac{5*5}{4*5}\)       (Luke)
\(\frac{7*4}{5*4}\)       (Darren)
\(\frac{25}{20}\)          (Luke)
\(\frac{28}{20}\)          (Darren)

\(\frac{28}{20}  >   \frac{25}{20}\)
        Darren           >            Luke
  
By:
\(\frac{28}{20}\) - \(\frac{25}{20}\) = \(\frac{3}{20}\)
Which is also by 0.15 m
Darren jumps higher and by 0.15 m