If 9999=4

8888=8

1818=4

1212=0

then 1919=?

**How?**

If you observe carefully, right side number is equal to total number of circles in the left side numbers. thus the answer to 1919 should be 2.

For 9999, there are 4 closed regions (consider the top part of the digit 9) and no other digits, so 9999=4

For 8888, there are 8 closed regions (consider the top part and the bottom part of the digit 8) and no other digits, so 8888=8

For 1816, there are 3 closed regions (2 of the digit 8 and 1 of the digit 6) and 2 other digits, so 1816=3*2=6

For 1212, there are 0 closed regions (digits 1 and 2 do not have closed regions) and 4 other digits, so 1212=0*4=0

Use same calculation for 1919, there are 2 closed regions (digit 9) and 2 other digits, so 1919=2*2=4

Given a number N, f(N) is defined as follows:

Count the number of closed regions for each digit of N, and get total T.

If every digit has closed regions, then f(N)=T

Else if R digits do not have closed regions, then f(N)=T*R

So f(9999)=4 and f(8888)=8 and f(1816)=6 and f(1212)=0 and f(1919)=4.

- All categories
- Pre-Algebra Answers 12.3k
- Algebra 1 Answers 25.3k
- Algebra 2 Answers 10.5k
- Geometry Answers 5.2k
- Trigonometry Answers 2.6k
- Calculus Answers 6.1k
- Statistics Answers 3k
- Word Problem Answers 10.2k
- Other Math Topics 6.7k

81,977 questions

86,376 answers

2,240 comments

72,117 users