Answer: So, the probability will be

Step-by-step explanation:
Since we have given that
Number of blue balls =30
Number of red balls = 40
Number of white balls = 30
Since there are 100 balls in total ,
As we have given that there is no white ball chosen.
So, only 70 balls are left with us , from which we choose a blue ball
So, the probability will be

Answer:
4×30+5×30=120+150=270
Step-by-step explanation:
looking at the last row, we can see that the total number of students will be 4×30+5×30=120+150=270
Answer:
BD = 4.99
Step-by-step explanation:
You can simply use the trigonometric identity tangent to solve for length BD.
Tan = opposite/adjacent
In this case we have,
Tan 31 = 3/BD
BD = 3/Tan 31
BD = 4.99
I think what the teacher wants to express is that SI units are much more convenient to use than English units because the prefixes of the metric system will give you an idea on the conversion factor. Unlike English units, like ft to yard, there is no prefix to help you. You have to know the fact that 1 yard is equal to 3 feet.