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45 MINUTES. METHOD 1 LET US TALK ABOUT 24 HOURS AS IT WILL SIMPLIFY THE PROBLEM. IN 24 HOURS: THE COLD TAP WILL BE ABLE TO FILL THE BATHTUB 80 TIMES. THE HOT TAP WILL BE ABLE TO FILL THE BATHTUB 96 TIMES. THE DRAIN WILL BE ABLE TO DRAIN THE BATHTUB 144 TIMES. THUS IN 24 HOURS, THE BATHTUB WILL BE FILLED 80 + 96 - 144 = 32 TIMES (IF BOTH TAPS ARE TURNED ON WITH THE PLUG LEFT OUT) THUS IT WILL TAKE 45 MINUTES TO FILL THE TUB ONCE. METHOD 2 THE BATHTUB FILLING RATE IS: THE COLD TAP WILL FILL THE BATHTUB AT 1/18 TUB/MINUTE THE HOT TAP WILL FILL THE BATHTUB AT 1/15 TUB/MINUTE THE DRAIN WILL DRAIN THE BATHTUB AT 1/10 TUB/MINUTE THE NETT BATHTUB FILL RATE IS: 1/18 + 1/15 - 1/10 = 1/45 TUB/MINUTE THE WATER WILL FILL 1/45 OF THE TUB IN 1 MINUTE, SO THE TUB WILL BE FULL IN 45 MINUTES A = 3.5 B = 4.5 C = 9.5 D = 3.5 TO SOLVE THE PUZZLE, YOU WILL NEED TO COME UP WITH 4 EQUATIONS: A + B = 8 ... (1) C - D = 6 ... (2) A + C = 13 ... (3) B + D = 8 ... (4) SUBTRACTING (1) FROM (3) GIVES: C - B = 5 ... (5) ADDING (2) TO (4) GIVES: B + C = 14 ... (6) ADDING (5) AND (6) GIVES: 2C = 19 C = 9.5 SUBSTITUTING C = 9.5 IN (2) GIVES: 9.5 - D = 6 D = 3.5 SUBSTITUTING D = 3.5 IN (4), GIVES: B + 3.5 = 8 B = 4.5 SUBSTITUTING B = 4.5 IN (1), GIVES: A + 4.5 = 8 A = 3.5 THE ELDEST IS 8 YEARS OLD AND THE 2 YOUNGER ONES ARE 3 YEARS OLD. LET'S BREAK IT DOWN. THE PRODUCT OF THEIR AGES IS 72. SO THE POSSIBLE CHOICES ARE: 2, 2, 18 - SUM(2, 2, 18) = 22 2, 4, 9 - SUM(2, 4, 9) = 15 2, 6, 6 - SUM(2, 6, 6) = 14 2, 3, 12 - SUM(2, 3, 12) = 17 3, 4, 6 - SUM(3, 4, 6) = 13 3, 3, 8 - SUM(3, 3, 8 ) = 14 1, 8, 9 - SUM(1,8,9) = 18 1, 3, 24 - SUM(1, 3, 24) = 28 1, 4, 18 - SUM(1, 4, 18) = 23 1, 2, 36 - SUM(1, 2, 36) = 39 1, 6, 12 - SUM(1, 6, 12) = 19 THE SUM OF THEIR AGES IS THE SAME AS YOUR BIRTH DATE. THAT COULD BE ANYTHING FROM 1 TO 31 BUT THE FACT THAT JACK WAS UNABLE TO FIND OUT THE AGES, IT MEANS THERE ARE TWO OR MORE COMBINATIONS WITH THE SAME SUM. FROM THE CHOICES ABOVE, ONLY TWO OF THEM ARE POSSIBLE NOW. 2, 6, 6 - SUM(2, 6, 6) = 14 3, 3, 8 - SUM(3, 3, 8 ) = 14 SINCE THE ELDEST KID IS TAKING PIANO LESSONS, WE CAN ELIMINATE COMBINATION 1 SINCE THERE ARE TWO ELDEST ONES. THE ANSWER IS 3, 3 AND 8 THE SON WILL CATCH UP WITH HIS FATHER IN 10 MINUTES. IN 10 MINUTES, THE SON WOULD HAVE TRAVELED HALF THE DISTANCE, SINCE HIS TOTAL TRAVELING TIME IS 20 MINUTES. THE FATHER STARTED 5 MINUTES EARLIER THAN THE SON, SO HE WOULD HAVE TRAVELED FOR A TOTAL OF 15 MINUTES WHEN HIS SON REACHED HIM. THEREFORE, THE FATHER WOULD HAVE ALSO TRAVELED HALF THE DISTANCE IN 15 MINUTES