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# The sum of father's and mother's ages is 84. if the age of father 5 years ago is the same as the age of mother 3 years later, how old is father now?

step-by-step explanation: step 1: find the number of terms

the nth term of an arithmetic sequence is given by

t

n

=

a

+

(

n

1

)

d

. we know

t

n

(-57), r (-5) and a (8), however we don't know n. we will therefore solve for

n

.

57

=

8

+

(

n

1

)

5

57

=

8

5

n

+

5

57

13

=

5

n

70

=

5

n

n

=

14

the sequence has

14

terms.

step 2: apply the formula for sum:

when dealing with arithmetic series, we will frequently use two formulas to help us find the sum. they are:

s

n

=

n

2

(

2

a

+

(

n

1

)

d

)

s

n

=

n

2

(

a

+

t

n

)

since we know the first term, the last term and the number of terms, we have enough information to use the latter; this one is more efficient and easy to use than the first.

s

n

=

n

2

(

a

+

t

n

)

s

14

=

14

2

(

8

+

(

57

)

)

s

14

=

7

(

8

57

)

s

14

=

343

hence, the sum of this arithmetic sequence is

343

.

practice exercises:

determine the sum of the following sequence:

3

,

14

,

25

,

,

179

hopefully this helps, and good luck!

dikit dikit mo nalang bawal kasi naka higa eh

• Réponse publiée par: shannel99
1. g/f
2. f*g
3. fog
4. f+g
5. f/g
6. f-g
• Réponse publiée par: jemuelpogi
Interest = 51,200 - 40,000
=11,200

time = i/(pr)
= 11,200/(40,000)(0.12)
= 11,200 / 4,800
= 2.33 or 2 years and 4 months
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The sum of father's and mother's ages is 84. if the age of father 5 years ago is the same as the age...