Thoh:
4 kids: 5, 2, 2, 1
has to be 4 kids.... less than five, and 2 middle kids
youngest is 1, and 2 middle are B and B, and oldest is A years old
AB^2 = 2(A + 2B + 1)
A = (4B+2)/(B^2-2)
then i used a graphing calculator to find integer A when B is an integer and got my answer
Nice and logical.
For those with only pen and paper:
Age possibilities:
3 6 *
4 4 *
1 3 8 **
1 4 5
2 2 4 *
1 1 4 6 **
1 2 2 5
1 2 3 3 **
2 2 2 2 *
* eliminated due to youngest(s) being 1 (wife gave birth a year ago).
** eliminated: if number on the door was equal to oldest, then John would know.
So, it's 1-4-5 or 1-2-2-5; 1-2-2-5 is it, due to "two in the middle"...
RAIN
132
Wow! That was a lucky guess of mine

. I wonder how many ways there are to reach the same conclusion. I think I have it as:
R = Rain speed
T = Trys speed
A = hours to empty C1
B = hours of rain in C3
C = hours to empty C3 (Note: AR means A*R)
Try enters C1 at hour 8
Gallons already in C1 : 7R
Rain while Try empties: AR
Trys emptying of C1 : AT
so: AT = 7R + AR ; T / R = (A + 7) / A (1)
Try empties C2 in 42 hours
Gallons already in C2 : R(A + 49)
Rain while Try empties: 42R
Trys emptying of C2 : 42T
so: 42T = R(A + 49) ; T / R = (A + 49) / 42 (2)
(1) (2) : (A + 7) / A = (A + 49) / 42
A^2 + 7A - 294 = 0
(A + 21)(A - 14) = 0 ; A = 14 (3)
(1) (3) : 2T = 3R
Try empties C3; both speeds double
Gallons already in C3 : R(A + 49) = 63R
Rain while Try empties : 2RB
Trys emptying of C3 : 3RC
so: 3RC = 2RB + 63R ; C = (2B + 63) / 3 (4)
Try empties C1 and C2 in 44 hours, normal speed
Gallons now in C1 and C2: R(42 + 4B)
Trys emptying of C1/C2: 44(3R / 2)
so: R(42 + 4B) = 44(3R / 2) ; B = 6 (5)
(4) (5) C = 25
Hour at which Try enters C3 : 7 + 14 [A] + 42
= 63
Hour at which rain stopped : 7 + 14 + 42 + 6
.= 69
Hour at which Try is finished: 7 + 14 + 42 + 25 [C] + 44 = 132
It is starting to rain on Marks parade:
-open-top empty container C is outside
-at 0 hours, a steady heavy rain starts
-rain enters C at rate of R gallons per hour (gph)
-Mark jumps in C as soon as the rain starts
-Mark takes water out at 1/6 R gph for 9 hours
-at this point, rain slows to 1/3 R gph, and Mark triples his speed
-13 hours later, the rain stops
-at this point, Mark reduces his current speed by 8 gph,
and empties C in 10 hours
OK; if Mark handled a total of 778 gallons in this 32 hour period, what is the size of C in gallons, and the rain speed at start