DIY Challenge 2: Strategy for 9 bars!
Can you find the real gold bar in 2 turns? Share your different strategies to do it.
Link to the Activity: Click Here
What students worked out6
Student 7
YES WE CAN FIND THE REAL BAR IN 2 TURNS,HOW? WE PUT 1,2,3 ONE SIDE AND 4,5,6 ON THE OTHER LETS TAKE THEY ARE EQUAL THEN ONLY THREE ARE LEFT 7,8 & 9,THEN WE PUT 7 ON ONESIDE AND 8 ON THE OTHER THEN WE KNOW WHICH IS THE REAL GOLD BAR
Student 1
I found a way but it takes 3 turns if lucky 2 if super lucky 1 turns first we weigh 1234vs5678 if equal then 9 if not then lets say 5678 is heavier then we weigh 5vs6 if equal weigh last numbers remaining in this case 7vs8 then whichever is heavier is the real gold bar if 5vs6 one of them turns out to be heavier then whichever of them is heavier is the real gold bar
Student 4
We can first weigh ingots 1,2,3,4 and 5,6,7,8. If they weigh the same, 9 is the real ingot. If ingots 1,2,3 and 4 weigh more, we weigh 1,2 and 3,4. If 3,4 is heavier, we weigh three and four to see which is the heaviest of the 2. If 3 is heavier, 3 is the real ingot.
If my answer is unclear, Ican explain in the class on Sunday
Student 3
Strategy is same as that of 8 bars.Minimum 2 weighing required
Put 123 on 1 side and 456 on other side.
If 123>456 then weigh 1 and 2 and decide which one is gold bar.
If 123 < 456 the we will weigh 4 and 5.
If 123 = 456 then we will 7 and 8.
If 7 = 8 then 9 is gold.Student 3
from 4 to 9 bars minimum 2 weighing required without considering luck.
for 7,8, 9 bars you can make 3 groups with 3 bars in at least 2 groups
so that you can weigh and find out gold bar in minimum 2 attempts
Student 2
FOR 9 WE WILL DO 4 TO 4 IF THEY ARE SAME THE REMAINING BAR IS THE ANSWER IF NOT THE HEAVIER 4
THEN WE HAVE 4 THEN 2 TO 2 THEN 1 TO 1