Three kids play tennis at the same tennis courts. Mark plays every fourth day, David plays every seventh day and Bryan plays every sixth day. All of them were at the tennis court on Wednesday, July 18th. What will be the next day, when all three of them will be at the court together?

Wednesday (9 weeks later) = 10th October.

Step-by-step explanation:

We label the days with the initials of the names.

M = 4

D = 7

B = 6

LCM of 6 + 7 = 42

LCM of 6+7 + 4 = 84

We find 84 is the amount of days we need to add on to july 18th

We first find the weeks 84/7 = 9 weeks.

As Wednesday July 18th is exclusive it would be 84 days after this event.

18 + 84 = 102 days.

31 days in july = 31

31 days in Aug = 31

30 days in Sept = 30

= 92

102-92 = 10

We now know date is Wednesday 10th October

We can check 84 days = 9 weeks

13 days in July makes 31st july

31 days in Aug makes 31st Aug

30 days in Sept makes 30th Sept

= 74 days + 10 days = 84

10th October is the checked date and we know it is also a Wednesday as Wednesday had stayed exclusive and prove that there are 7 days in the week to account x 9, to account for an exact 9 weeks later duration.

Wednesday, October 10

Step-by-step explanation:

David play every 7 days, so since the first day is a Wednesday, David plays every Wednesday. We need to find the smallest common multiple of 4 and 6 that is also a multiple of 7. Since 4 * 3 = 12 and 6 * 2 = 12, we see that all multiples of 12 are also multiples of 4. We list the multiples of 12:

12, 24, 36, 48, 60, 72, 84, 96, ...

The smallest multiple of 12 that is a multiple of 7 is 84.

The first day all of them play together after July 18th is 84 days later.

84/7 = 12

We look in a calendar, and we see that exactly 12 weeks after July 18 is Wednesday, October 10.

Answer: Wednesday, October 10.