<prompt> Bala kakaretso ea letoto 1 4 7 10 ... 91nan  <response>: Instruction in English: Calculate the sum of the series 1 4 7 10 ... 91 . Response in English: The given series is an arithmetic sequence with the first term as 1 and a common difference of 3. The nth term of the given series can be calculated using the formula an a1 n - 1d where a1 1 and d 3. Lets find the number of terms in the given series:an a1 n - 1d91 1 n - 1391 - 1 3n - 190 3n - 3n 90 3 3n 31The sum of the arithmetic sequence is given by the formula Sn n2 a1 an.Substituting the values for the given series, we get S31 312 1 91 1431.Therefore, the sum of the series 1 4 7 10 ... 91 is 1431. . Response in Sesotho: Letoto le fanoeng ke tatellano ea lipalo ka nako ea pele e le 1 le phapang e tloaelehileng ea 3. Nako ea nth ea letoto le fanoeng e ka baloa ho sebelisoa foromo e a1 n - 1d moo a1 1 le d 3. A re fumaneng palo ea mantsoe letotong le fanoeng: an a1 n - 1d 91 1 n - 13 91 - 1 3n - 1 90 3n - 3 n 90 3 3 n 31 Kakaretso ea tatellano ea lipalo e fanoa ka foromo Sn n2 a1 an. Ho fetola litekanyetso tsa letoto le fanoeng, re fumana S31 312 1 91 1431. Ka hona, kakaretso ea letoto la 1 4 7 10 ... 91 ke 1431. 