There were 75 pebbles in Boxes A, B and C. After moving 28 pebbles from Box A to B, 24 pebbles from B to C, and 19 from C to A, there was an equal number of pebbles in each box. How many pebbles were in Box A in the beginning?
+130511 Alan's answer is more "mathematical" than mine, but.....
Notice that Box B picks up a net of 4 pebbles.......and since each box must contain 25 pebbles at the end, Box B must have had 21 pebbles at the start.
And Box C picks up a net of 5 pebbles......so it must had 20 at the start.
Then A must have contained 75 - 21 - 20 = 34 at the start
+33661 A + B + C = 75
A - 28 +19 = 75/3
A - 9 = 25
A = 34
B - 24 + 28 = 75/3
B + 4 = 25
B = 21
C - 19 + 24 = 75/3
C + 5 = 25
C = 20
.
+130511 Alan's answer is more "mathematical" than mine, but.....
Notice that Box B picks up a net of 4 pebbles.......and since each box must contain 25 pebbles at the end, Box B must have had 21 pebbles at the start.
And Box C picks up a net of 5 pebbles......so it must had 20 at the start.
Then A must have contained 75 - 21 - 20 = 34 at the start
