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= 510

Step-by-step explanation:

Formula for the sum of n terms of a finite arithmetic series is

S_n=\dfrac{a_1+a_n}{2}\cdot n.

If n=10,\ a_1=13,\ a_{10}=89, then

S_{10}=\dfrac{13+89}{2}\cdot 10=51\cdot 10=510.

d. bc = 12 and ef = 16

step-by-step explanation:

we are given that δabc : δdef such that .

also, it is given that

so, from the options, we need that .

a.

b.

c.  

d.

as, we can see that only option d gives the same ratio as i.e. .

hence, the possible lengths are bc = 12 and ef = 16.

fahrenheit

step-by-step explanation:

fahrenheit is more precise than celsius. the ambient temperature on most of the inhabited world ranges from -20 degrees fahrenheit to 110 degrees fahrenheit—a 130-degree range. on the celsius scale, that range is from -28.8 degrees to 43.3 degrees—a 72.1-degree range. this means that you can get a more exact measurement of the air temperature using fahrenheit because it uses almost twice the scale.