Answer:
x=3 and x=-1.25
Step-by-step explanation:
4x^2-7x=15
subtract 15 from each side:
4x^2-7x-15=0
factor (trying different numbers that the sum is 7 and the quotient is 15)
(2x-6 )(2x+2.5 )=0
2x-6=0 add 6 to each side
2x=6
x=3
2x+2.5=0 subtract 2.5 from each side
2x=-2.5
x=-1.25
D. 1mm/10cm is the correct answer choice.
Answer:
a) 62
b) 31/45
Step-by-step explanation:
a) The table tells you there are 42 males, and 20 more females that study biology.
42 +20 = 62 . . . are male or study biology or both
__
b) Of the total of 90 people, 62 are male or study biology (or both). The probability that any person is in that category is ...
62/90 = 31/45 = P(male or biology)
The question is incomplete, here is the complete question:
The half-life of a certain radioactive substance is 46 days. There are 12.6 g present initially.
When will there be less than 1 g remaining?
<u>Answer:</u> The time required for a radioactive substance to remain less than 1 gram is 168.27 days.
<u>Step-by-step explanation:</u>
All radioactive decay processes follow first order reaction.
To calculate the rate constant by given half life of the reaction, we use the equation:
where,
= half life period of the reaction = 46 days
k = rate constant = ?
Putting values in above equation, we get:
The formula used to calculate the time period for a first order reaction follows:
where,
k = rate constant =
t = time period = ? days
a = initial concentration of the reactant = 12.6 g
a - x = concentration of reactant left after time 't' = 1 g
Putting values in above equation, we get:
Hence, the time required for a radioactive substance to remain less than 1 gram is 168.27 days.
What is the mean of this data set? 12,17,16,10,20,13,14,14,12,12,19,18
Gemiola [76]
Answer:
14.75 :) please give me brainliest :)
Step-by-step explanation: