Math Figure it out

            Math Figure out

his plant had grown by 2.4cm. If his plant was 1.7 cm last time they checked, how much had the plant grown?

How it works? You cannot do a cm by 24 if you want a decimal add a decimal point to it (example)( 2.4cm).

How i worked it out! I could either take away the 4 from 2.4 Which will be 0.4 which is 2.0,then take away 0.3 from 2.0 which gets 1.7cm

             (A)          2.4 cm - 0.7 = 1.7cm

                 

                           2.4cm - 0.4 = 2.0cm

                          2.0cm - 0.3 = 1.7