Find the sum of the following without actually adding: 1+3+5+7+9+11+13+15

Mathematics

2 answers:

-Dominant- [34]2 years ago

7 0

Answer:

Step-by-step explanation:

The following numbers are successive odd numbers.

The sum of successive odd numbers (starting from 1) is always the square of number of terms you are adding.

Hear there are 8 terms. Square of 8 is 64.

Hence the sum of this numbers is 64.

I am Lyosha [343]2 years ago

6 0

use this formula Sn=n/2[2a+(n-1)d]

here,d=a2-a1 and n= no. Of terms

Step-by-step explanation:

S8=8/2[2(1)+(8-1)2]

S8=64

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dem82 [27]

9514 1404 393

Answer:

(b) 15.32

Step-by-step explanation:

You can use your triangle sense to answer this.

The side x will always be shorter than the hypotenuse, 20. This eliminates the last two choices.

If the angle is 45°, then the sides are equal at about 0.707 times the length of the hypotenuse. That would make them 0.707×20 = 14.14. Since the angle is greater than 45°, the opposite side will be greater than 14.14. Only one answer choice fits between 14 and 20: the second choice -- 15.32.

The mnemonic SOH CAH TOA reminds you of the relation ...

Sin = Opposite/Hypotenuse

sin(50°) = x/20

x = 20×sin(50°) . . . . multiply by 20 to find x

x ≈ 15.32 . . . . . . . . . use your calculator to evaluate

The attachment is intended to show how the triangle side lengths change with angle.