Question

Ninhydrin’s composition is 60.68 % carbon, 3.40% hydrogen and 35.92 % oxygen.
What is the empirical formula?

Answer 1

we have approximately
C5 H7/2 O9/4
or
C20 H14 O9
That would give a mol wt of
12*20 + 14 + 9*16 = 398
240/398 = 60.3%
14/398 = 3.5%
144/398 = 36.2%
pretty close

Answer 2

Good math solution.
There is a chemistry solution if you have an interest in seeing it.