First difference,

Second difference,

Third difference,

And so on.
Assuming the pattern holds on, we see that
i-th difference,


Then, nth term is,











Now, the 21st term in the sequence is,



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You are right the answer is D below is the solution:
<span>9.2 + 13.6 + 56.7 = 79.5</span>
Answer:

Step-by-step explanation:
Given that the base area of the cuboid is 7cm² . And it's volume is 21cm³ . We need to find its total surface area . Now here we need to find the height . We can find height as ,
<u>Height</u><u> </u><u>:</u><u>-</u>
Let's find out the Total surface area .
<u>TSA </u><u>of </u><u>cuboid</u><u> </u><u>:</u><u>-</u><u> </u>
<u>Put </u><u>on</u><u> the</u><u> respective</u><u> values</u><u> </u><u>:</u><u>-</u><u> </u>

Answer:
Two semi circles would equal one circle.
The perimeter of a circle is PI x diameter.
The diameter of the circle is shown as 56 m
The perimeter of the 2 ends = 56 x 3.14 = 175.84
The length of the inside of the track is given as 130 m, and there are 2 sides so 130 + 130 = 260 m.
Total perimeter = 260 + 175.84 = 435.84 m.
Step-by-step explanation: