Will give

there are 25 horses.
what is the minimum number of races needed so you can identify the fastest 3 horses? you can race up to 5 horses at a time, but you do not have to watch.

7 races.

Step-by-step explanation:

Make group of 5 horses and run 5 races. Suppose five groups are a,b,c,d,e and next alphabet is its individual rank in this group(of 5 horses).for eg. d3 means horse in group d and has rank 3rd in his group. ( 5 races done)

a1 b1 c1 d1 e1

a2 b2 c2 d2 e2

a3 b3 c3 d3 e3

a4 b4 c4 d4 e4

a5 b5 c5 d5 e5

Now make a race of (a1,b1,c1,d1,e1).(Race 6 done) suppose result is a1>b1>c1>d1>e1

which implies a1 must be FIRST.

b1 and c1 MAY BE(but not must be) 2nd and 3rd.

FOR II position, horse will be either b1 or a2

(we have to find top 3 horse therefore we choose horses b1,b2,a2,a3,c1 do racing among them (Race 7 done)

The only possibilities are :

c1 may be third

b1 may be second or third

b2 may be third

a2 may be second or third

a3 may be third

The final result will give ANSWER. suppose result is a2>a3>b1>c1>b2

then answer is a1,a2,a3,b1,c1.

Hence,

The answer is 7 races.

b. x + 1

step-by-step explanation:

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