Tina had 20 m 5 cm long cloth. She cuts 4 m 50 cm length of cloth from this for making a curtain. How much length of cloth is left with her?

Total length of cloth = 20 m 5 cm

= 20 m + $\dfrac{5}{100}$ m = 20 m + 0.05 m = 20.05 m

Length of cloth cut for curtain = 4 m 50 cm

= 4 m + $\dfrac{50}{100}$ m = 4 m + 0.50 m = 4.50 m

Length of cloth left = 20.05 - 4.50

Writing in column form and subtracting:

$\begin{array}{r} \phantom{+}20.05 \ -\space 4.50 \ \hline 15.55 \end{array}$

Hence, the length of cloth left with Tina is 15.55 m or 15 m 55 cm.