Question

There are eight bags of rice looking alike, seven of which have equal weight and
one is slightly heavier. The weighing balance is of unlimited capacity. Using this
balance, the minimum number of weighings required to identify the heavier bag is
(A) 2 (B) 3
(C) 4 (D) 8

Answer 1

Answer:

2 Weighing

Step-by-step explanation:

There are eight bags of rice looking alike, seven of which have equal weight and  one is slightly heavier. The weighing balance is of unlimited capacity.

Bags are B1 , B2 , B3 , B4 , B5 , B6 , B7 , B8

lets put

weiging 1 :

Put B1 , B2  , B3   one side &  B4 ,B5 , B6 another side

Case 1 if found equal

then

weighing 2 :  B7 one side & B8 other side  and find heavier Bag

Case 2 Either of 1 is heavier

Let say B1 , B2  , B3  is heavier

then

Weighing 2  :   B1 one side  , B2 other side

if one is found heavier then that is heavy bag   otherwise B3 is heavier

similarly for (B4 , B5 & B6)

so Only 2 Weighing is required

option A is correct

Answer 2

Answer:

3

Step-by-step explanation:

Let 8 bags be A, B, C, D, E, F, G & H.

Step 1 :- Take A,B&C on one weighing plate and D,E&F on another plate.

Step 2 :- There are 3 cases in this situation :-

Case (a) :- If A,B&C carrying plate goes down weigh A&D and B&E. If A&D carrying plate goes down then A is the heaviest bag, if B&E carrying plate goes down then B is the heaviest bag & if both the plates are at equal level then C is the heaviest bag.

Case (b) :- If D,E&F carrying plate goes down weigh D&A and E&B. If D&A carrying plate goes down then D is the heaviest bag, if E&B carrying plate goes down then E is the heaviest bag & if both the plates are at equal level then F is the heaviest bag.

Case (c) :- If A,B&C and D,E&F carrying plates are at equal level then weigh G and H. If G carrying plate goes down then G is the heaviest bag and if H carrying plate goes down then H is the heaviest bag.