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Erase a prime (Posted on 2020-08-03)

Write down the first n primes.

Erase one of them and the mean of the remaining numbers is 10.

What number did you erase?

No Solution Yet Submitted by Jer

Rating: 3.0000 (1 votes)

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computer solution

| Comment 1 of 5

10 for N=1 to 100

20 P=nxtprm(P)

30 Tot=Tot+P

40 for I=1 to N

50 T=Tot-prm(I)

55 if N>1 then

60 :Avg=T/(N-1)

70 :if Avg=10 then print I,prm(I),N,P

80 next

90 next

finds

4 7 8 19

meaning,

erase the 4th prime, 7, from the first 8 primes, the last of which is 19.

2 + 3 + 5 + 11 + 13 + 17 + 19 = 70 checks out

Posted by Charlie on 2020-08-03 13:45:23

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