Question

A monkey climbs $30$ feet at the beginning of each hour and rests for a while when he slips back $20$ feet before he again starts climbing I the beginning of the next hour. If he begins his ascent at $8.00$ am, at what time will he first touch a flag at $120$ feet from the ground?

• A. $4$ pm
• B. $5$ pm
• C. $6$ pm
• D. $3$ pm

Answer 1

The correct option is C $6$ pm

Net ascent of monkey in $1$ hr$=(30-20)=10$ feet.
So, the monkey ascends $90$ feet in $9$ hours, i.e., till $5$ p.m. Clearly, in the next $1$ hour i.e, by $6$ pm the monkey ascends remaining $30$ feet to touch the flag.
Hence, option $C$ is the correct answer.