What are the highest and lowest numbers you can possibly score?

Question

Assume you are using a basic calculator and press the numbers in the order shown. Each question mark should be replaced with a mathematical sign. Plus, minus, multiply and divide can each be used once only.

What are the highest and lowest numbers you can possibly score?

3 ? 8 ? 2 ? 5 ? 8 = ?

Answer 1

Basic calculator will give these results, 27 being the highest and -21 being the lowest:
3/8-2+5*8 = 27
3-8/2+5*8 = 20
3+8*2+5-8 = 19
3*8/2-5+8 = 15
3+8-2/5*8 = 14.4
3*8-2/5+8 = 12.24
3*8/2+5-8 = 9
3-8*2/5+8 = 6
3+8-2*5/8 = 5.625
3+8/2-5*8 = 4
3/8+2*5-8 = 3.875
3/8*2-5+8 = 3.75
3*8-2+5/8 = 3.375
3*8+2-5/8 = 2.625
3+8/2+5-8 = 2.5
3+8*2-5/8 = 2.125
3/8-2*5+8 = -0.125
3-8*2+5/8 = -0.625
3-8+2*5/8 = -1.875
3/8*2+5-8 = -2.25
3*8+2/5-8 = -2.8
3-8/2*5+8 = -4.5
3-8+2/5*8 = -4.8
3/8+2-5*8 = -21