CAT Quant · Chapter Test
Arithmetic Progression — 25-Question Test
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Formula Reference Sheet
This chapter
Term & general form
| nth term | a_n = a + (n − 1)d |
|---|---|
| Common difference | d = a_n − a_(n−1) |
| Number of terms | n = (last − first)/d + 1 |
| mth from the end | l − (m − 1)d (l = last term) |
| Neighbour-average property | a_n = (a_(n−1) + a_(n+1)) / 2 |
Sum & shortcuts
| Sum of n terms | S_n = n/2 [2a + (n − 1)d] |
|---|---|
| Sum via first & last | S_n = n/2 (first + last) |
| Sum from average | S_n = n × (average term) |
| First n naturals | 1 + 2 + … + n = n(n + 1)/2 |
| First n odd numbers | 1 + 3 + … + (2n − 1) = n² |
CAT reference
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