What number could be added to 0.40 ml for the level of precision to be 0.01ml

- 0.39

Step-by-step explanation:

Level of precision = 0.01 mL

We need to find a number which could be added to 0.40 mL for the level of precision to be 0.01 mL .

Let x be a number  which could be added to 0.40 mL for the level of precision to be 0.01 mL .

On subtracting 0.40 from both sides , we get

On solving , we get

We know that where 0 is the additive inverse .

So,

Here ,

Therefore ,

Therefore , -0.39 could be added to 0.40 mL for the level of precision to be 0.01mL

answer: b

step-by-step explanation:

let x and 400 - x be the two numbers.  

==> 0.80x + 0.85(400 - x) = 400 - 68 from the statement of the problem.  

< ==> 0.80x + 0.85(400 - x) = 400 - 68  

==> 340 - 0.05x = 332  

< ==> -0.05x = -8 ==> x = 160, the first number ==> 400 - x = 240, the second number.