Answer:
143
Step-by-step explanation:
90-53=37
180-37=143
Answer:

Step-by-step explanation:
In scientific notation, the national debt in 2013 was approximately

You can see this by taking the decimal point between the 1 and 6 and moving it 13 places to the right.
The smallest power of 10 that will be larger than this number is
.
Answer:
She purchased 4 pencils
Step-by-step explanation:
Here, we are to calculate the number of pencils bought given the information in the question.
The amount per pencil is $0.91. The total amount of this since she bought x number of pencils is $0.91 * x = $0.91x
Now, after paying $10, she was given $6.36 as change
what this means is that what the pencils cost is 10-6.36 = $3.64
Now we equate the cost in terms of x to this;
0.91x = 3.64
x = 3.64/0.91
x = 4 pencils
Answer:

Step-by-step explanation:
A rectangle is a closed planer quadrilateral with four right angles and its opposite sides are the same length. The fence around it including the gates is 200 feet long, so basically they are providing the perimeter of the rectangle. The perimeter of a rectangle is equal to the sum of all its sides. Hence:

The ectangular playground is 40 feet wide, so:

Therefore:

Solving for h:

The area of a rectangle is equal to the product of two of its contiguous sides, hence:

I attached you a picture of the rectangle
Answer: A) 
B) H = 5.10
C) Yes
Step-by-step explanation: <u>Exponential</u> <u>Decay</u> <u>function</u> is a model that describes the reducing of an amount by a constant rate over time. Generally, it is written in the form: 
A) C is initial quantity, in this case, the initial concentration of DDT. To determine r, using the data given:



Using a natural logarithm property called <em>power rule:</em>



The decay function for concentration of DDT through the years is 
B) The value of H is calculated by 


Again, using power rule for logarithm:



H = 5.10
Constant H in the half-life formula is H=5.10
C) Using model
to determine concentration of DDT in 1995:

y(24) = 0.5
By 1995, the concentration of DDT is 0.5 ppm, so using this model is possible to reduce such amount and more of DDT.