Question

(1) If a man takes 3 min to walk down a street 258 m long, find his speed in km/h.
(11) A car covers 300 m in 20 s. Find its speed in km/h.
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Answer 1

Answer:

Sum of the First n Terms of a Series

The sum of the terms of a sequence is called a series .

If a sequence is arithmetic or geometric there are formulas to find the sum of the first n terms, denoted Sn , without actually adding all of the terms.

(Note that a sequence can be neither arithmetic nor geometric, in which case you'll need to add using brute force, or some other strategy.)

Sum of the Terms of an Arithmetic Sequence (Arithmetic Series)

To find the sum of the first n terms of an arithmetic sequence use the formula,

Sn=n(a1 + a2)2 ,

where n is the number of terms, a1 is the first term and an is the last term.

Example 1:

Find the sum of the first 20 terms of the arithmetic series if a1=5 and a20=62 .

S20=20(5 + 62)2S20=670

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Step-by-step explanation: