Which of the following numbers will replace the question mark (?) in the given series?0.04, 0.12, 0.42, 1.68, 2.08, 10.4, ?

Let's investigate the operations between consecutive terms:$0.04\to 0.12$: $\times 3$ ($0.04\times 3=0.12$)$0.12\to 0.42$: $+0.30$$0.42\to 1.68$: $\times 4$ ($0.42\times 4=1.68$)$1.68\to 2.08$: $+0.40$$2.08\to 10.4$: $\times 5$ ($2.08\times 5=10.40=10.4$)Following this alternating pattern ($\times 3,+0.3,\times 4,+0.4,\times 5,\dots$), the next step must be addition:6. $+0.50$ Therefore, the missing number is:
$$10.4+0.5=10.9$$