Jogging program

After knee surgery, the trainer tells the man to slowly return to his jogging program. He suggests a jogging program for 12 minutes each day for the first week. After that, he suggests increasing the time by 6 minutes per week.

Find the number of minutes the man took on the 15th week of his training.

Correct answer:

x =  96 min

Step-by-step explanation:

$$\begin{gathered} a_1=12\text{min} \\ d=6\text{min} \\ n=15 \\ {a}_2=a_1+d=12+6=18\text{min} \\ {a}_3=a_2+d=18+6=24\text{min} \\ \dots \\ x=a_1+d\cdot (n-1)=12+6\cdot (15-1)=96\text{min} \end{gathered}$$

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