Hello, 

From the reaction below the corresponding moles can be worked out as follows:

(the plus and minus in the brackets of the reactions indicate the ions) 

Cr2O7(-2)+8H(+)+3HCOOH→2Cr3(+)+3CO2+

7H20

=>3 moles of formic acid reduces = 1 mole K2 Cr2 O7

=> 1 mole of formic acid reduce = (1/3) mole K2 Cr2 O7

Ans is 1/3 mole

Hope this helps...