用一根长是10米的绳子围着一根树绕4圈,还余3.72米.这棵树的直径是多少米?
(10-3.72)÷4÷3.14
=6.28÷4÷3.14
=0.5(米).
答:这棵树的直径是0.5米.
It will not be long _____man can harness the solar energy and make it serve mankind.
A.since
B.before
C.when
D.after
某地对100名儿童做蛔虫感染情况粪检,发现蛔虫感染者50名,估计蛔虫感染率99%可信区间为()
A.37%~63%
B.35%~65%
C.30%~70%
D.25%~75%
E.26%~74%