Every yearon her birthday,Lucy gets 1 yuan from her aunt for every year of her age,that is 1 yuan on her birthday,2 yuan
问题描述：
Every yearon her birthday,Lucy gets 1 yuan from her aunt for every year of her age,that is 1 yuan on her birthday,2 yuan on her second and so on.Justafter her last birthday,and realized it was 276 yuan in total.How old is Lucy?
先翻译,列算式,并说明理由.
答
每年lucy生日的时候她的aunt都给她钱.
1岁的时候给1块,2岁的时候给2块,以此类推,在lucy上次生日的时候发现总共已经有276块钱了,问lucy现在多大?
等差数列求和
假设上次是n岁生日,
(1+n)n/2=276
n^2+n=276
得出n=23
上次生日23,现在可以说是24岁了