21? × 216.5 = 2112.4
A. 18.9
B. 4.4
C. 5.9
D. 13.4
Answer: Option C
Solution (By Examveda Team)
$$\eqalign{ & {21^?} \times {21^{6.5}} = {21^{12.4}}.....\left[ {\because {a^m} \times {a^n} = {a^{m + n}}} \right] \cr & \Rightarrow {21^{? + 6.5}} = {21^{12.4}} \cr & \Rightarrow ? + 6.5 = 12.4 \cr & \Rightarrow ? = 12.4 - 6.5 \cr & \Rightarrow ? = 5.9 \cr} $$This Question Belongs to Arithmetic Ability >> Surds And Indices
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