Algebra

Arithmetic Progressions

Arithmetic Progressions: Level 3 Challenges

         

(1+3+5++pth)+(1+3+5++qth)=(1+3+5++rth) \left (1 + 3 + 5 + \ldots + p^\text{th} \right ) \\ + \\ \left (1 + 3 + 5 + \ldots + q^\text{th} \right ) \\ = \\ \left (1 + 3 + 5 + \ldots + r^\text{th} \right )

Given the above equation for positive integers p,q,rp,q,r with pthp^\text{th} term greater than 39.

What is the smallest possible value of the expression below?

pth term +qth term +rth term  \large p^\text{th} \ \text{term } + q^\text{th} \ \text{term } + r^\text{th} \ \text{term }

a(qr)p+b(rp)q+c(pq)r\dfrac{a(q-r)}{p} + \dfrac{b(r-p)}{q} + \dfrac{c(p-q)}{r}

In an arithmetic progression, the sum of the first p,q,rp, q, r terms are a,b,ca, b, c respectively. Compute the expression above.

Consider an arithmetic progression with 2 and 101 as its first term and last term respectively. If the sum of the first 5 terms of this arithmetic progression is 40, find the sum of the last 5 terms of this progression.

A1:2,9,16,,2+(10001)×7A2:3,12,21,,3+(10001)×9? \begin{array}{llllll} A_1 : & 2, & 9, & 16, \ldots , & 2 + (1000-1) \times 7 \\ A_2: & 3, & 12 , & 21, \ldots, & 3 + (1000-1) \times 9? \\ \end{array}

How many integers appear in both of the following arithmetic progressions above?

Details and assumptions

Since 2 appears in A1A_1 but not in A2A_2, it does not appear in both of the arithmetic progressions.

ab , ab , ab , a+b\large \frac ab \ , \ ab \ , \ a -b \ , \ a+b

Above shows real numbers that belong to an arithmetic progression in order. Find the next term of this sequence.

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