Questions

In vulcanization, cruder rubber is heated with 3% sulphur at about for 1200C for 2-3 hours.

Vulcanised rubber is a vastly improved product.

The logic in the given puzzle is 

4 + 4 = 4 * 4+1 = 4 * 5 = 20

5 + 5 = 5 * 5+1 = 5 * 6 = 30

6 + 6 = 6 * 6+1 = 6 * 7 = 42

7 + 7 = 7 * 7+1 = 7 * 8 = 56

Similarly

9 + 9 = 9 * 9+1 = 9 * 10 = 90.

This is a common error while compiling C program in Linux. This error occurs when you are using pthread_create function to create threads in your programs.

To fix this problem ensure following points:
Include header file pthread.h in your program.
Add –lpthread linker flag with compilation command.
1- Include Header file
#include <stdio.h>
#include <pthread.h>
...
...
2- Compile command
gcc main.c -o main -lpthread

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