1 7 8 , 5 6 , 3 0 , ?
What is the next number in this sequence?
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Simple and elegant. Can the same rule apply for all preceding terms? That is, does there exist a number before the number 1 7 8 ? Why or why not?
No preceding terms. 178 can be factored only as 2 * 89.
1 7 8 = 2 ∗ 8 9 , 8 9 isn't a 1-digit number, therefore the number before 1 7 8 doesn't exist.
What the .....
The same rule cannot be applied for preceeding terms because 178 is the product of the primes 89 and 2, and since the process involves multiplying each digit of a number, 892 would preceed 8 9 2=144
@Challenge Master, Since The Prime Factorization of 178 is 2 × 8 9 and 89 is not a 1 digit number, Hence, A number before 178 Doesn't exist. ⌣ ¨
I believe that for this kind of problem, the simplest solution is the best. However, I would like to propose an alternative solution that satisfies this pattern, including the 'no term could come before 178' condition.
Here is the solution:
Let n denote index of each term. For n = 1: a n = 1 7 8
For n > 1:
a n = n − 1 1 3 4 n + 1 5 4 − a n − 1 n − 1 1 3 4 n + 1 5 4 − a n − 1 × n a n − 1 ( n − 1 ) − 2 2 ( 7 − 2 n )
For instance:
a 2 = 2 − 1 1 3 4 ( 2 ) + 1 5 4 − 1 7 8 2 − 1 1 3 4 ( 2 ) + 1 5 4 − 1 7 8 × 2 1 7 8 ( 2 − 1 ) − 2 2 ( 7 − 2 ( 2 ) ) = 5 6
a 3 = 3 − 1 1 3 4 ( 3 ) + 1 5 4 − 5 6 3 − 1 1 3 4 ( 3 ) + 1 5 4 − 5 6 × 3 5 6 ( 3 − 1 ) − 2 2 ( 7 − 2 ( 3 ) ) = 3 0
Therefore,
a 4 = 4 − 1 1 3 4 ( 4 ) + 1 5 4 − 3 0 4 − 1 1 3 4 ( 4 ) + 1 5 4 − 3 0 × 4 3 0 ( 4 − 1 ) − 2 2 ( 7 − 2 ( 4 ) ) = 2 8
To sum up, except for 0, the other possible answer is 28 .
Multiply every digit in a number to get next number in sequence.
1x7x8=56,5x6=30 & 3x0=0. So, answer is 0.
see... 1 7 8=56, 5 6=30 and now 3 0= 0... so 0 is the answer
1 x 7 x 8 = 56 then 5 x 6 = 30 next 3 x 0 = 0 so next number is 0.
1 x 7 x 8 = 56 5 x 6 = 30 3 x 0 = 0 so easy
178,56,30,0
1st Term=178
2nd Term=1x7x8=56
3rd Term=5x6=30
4th Term=3x0=0
The heading says it all !!!!
Please change the title !
just multiply each number so that you can get the next number. Like 1st number is
178 so
1 *7 *8 =56 = 2nd number
56= 5*6= 30 3rd number
30=3*0= 0 next number
1 *7 *8 =56
5 * 6=30
3 * 0=0
The product of the digits of any number gives the next one
Just have to multiply last two digits of each number
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1 x 7 x 8 = 56
5 x 6 = 30
3 x 0 = 0