小學(xué)一年級(jí)奧數(shù)題:排隊(duì)報(bào)數(shù)

字號(hào):

排好隊(duì),來(lái)報(bào)數(shù),正著報(bào)數(shù)我報(bào)七,倒著報(bào)數(shù)我報(bào)九,一共多少小朋友?
    解答:正著數(shù)報(bào)了一次,倒著數(shù)又報(bào)了一次,所以我被加了兩次,應(yīng)該減一:7+9-1=15