She swim 20 laps every day for 18 training days
so total laps done last month = 20*18 = 360 laps
She will swim 3 more laps per training day and add more training days to her monthly schedule.
20 laps + 3 laps = 23 laps
(a)If Katie adds 5 training days to her schedule this month, will she swim 215 more laps?
18 days + 5 days more = 23 days
23 laps every day for 23 training days
so total laps = 23*23 = 529 laps. That is 169 more laps than 360 laps done last month. Hence she cannot swim 215 more laps
If Katie adds 10 more training days to her schedule this month, will she swim 215 more laps?
18 days + 10 days more = 28 days
23 laps every day for 28 training days
so total laps = 23*28 =644 laps. That is 284 more laps than 360 laps done last month. Hence she can swim 215 more laps
(c)If Katie adds 6 more training days to her schedule this month, will she swim 215 more laps?
18 days + 6 days more = 24 days
23 laps every day for 24 training days
so total laps = 23*24 =552 laps. That is 192 more laps than 360 laps done last month. Hence she cannot swim 215 more laps
Build an equation for finding the number of additional training days she needs to swim 215 more laps
Let x be the number of days more
So training days = 18 + x
215 more laps , so total laps = 360 + 215 = 575
3 more laps per training day so 20 + 3 = 23 laps per day
laps * training days = total laps
so equation becomes
23 * (18+x) = 575
Now solve for x
414 + 23x = 575
Subtract 414 from both sides
23x = 161
x= 7
so she needs 7 training days to swim 215 more laps