Step 1 :In a number guessing game, a random integer is chosen from 1 to 399. Two students and an instructor each get a guess at the number. The one who gets closest to the random number is the winner. The two students are considered a team, trying to beat the instructor.
Step 2 :For part a), the first student should choose a number that divides the range into two equal parts to cover the maximum possible range of numbers. Therefore, the middle number of the range from 1 to 399 should be chosen. The calculation is \((1+399)/2 = 200\).
Step 3 :For part b), if the first student chose the number 345, then the second student should choose a number that divides the remaining range into two equal parts. The remaining range is from 1 to 344 and from 346 to 399. The middle number of the larger range should be chosen to cover the maximum possible range of numbers. The calculation is \((1+344)/2 = 172.5\). Since only an integer can be chosen, either 172 or 173 should be chosen.
Step 4 :Final Answer: For part a), the first student should choose the integer \(\boxed{200}\) to give the team the best chance of winning the game. For part b), the second student should choose the integer \(\boxed{172}\) to give the team the best chance of winning the game.