Mr. Rr the Rreliable Rrobot has been programmed to whistle every $18$ seconds and do a jumping jack every $42$ seconds, starting from the moment he is turned on. (For example, he does his first jumping jack $42$ seconds after he is turned on.)

How many times during the first $15$ minutes after activation will Mr. Rr whistle and do a jumping jack at the same instant?

Question

Mr. Rr the Rreliable Rrobot has been programmed to whistle every $18$ seconds and do a jumping jack every $42$ seconds, starting from the moment he is turned on. (For example, he does his first jumping jack $42$ seconds after he is turned on.)

How many times during the first $15$ minutes after activation will Mr. Rr whistle and do a jumping jack at the same instant?

anonymous · Answer

pls help

mathmale · Answer

Please eliminate the dollar symbol ($); it does not belong here.
Have you tried drawing a diagram that shows where along the horizontal axis (representing time) this robot will be after each whistle, and also after each jumping jack?