《2025年心算口算巧算六年级上册北师大版》

1 求圆的面积或周长，写出计算过程。
(1)d＝10 m　　S＝
(2)d＝40 m　　C＝

答案：
(1)d=10m，r=5m
S=πr²=3.14×5²=3.14×25=78.5m²
(2)d=40m
C=πd=3.14×40=125.6m

2 计算下面各题。(能简算的要简算)
($\frac{1}{3}$－$\frac{1}{4}$)÷25%
($\frac{5}{7}$－$\frac{3}{14}$)÷45%
25%×$\frac{3}{8}$＋75%÷$\frac{8}{3}$
60%×$\frac{5}{6}$＋4÷$\frac{8}{5}$
$\frac{7}{8}$×$\frac{4}{21}$×$\frac{2}{3}$÷3
$\frac{12}{5}$×($\frac{5}{6}$＋$\frac{3}{4}$)＋$\frac{1}{3}$
$\frac{3}{4}$×$\frac{1}{3}$＋$\frac{1}{4}$×$\frac{1}{3}$－$\frac{1}{3}$
$\frac{5}{8}$×$\frac{4}{13}$×$\frac{1}{2}$÷5
$\frac{2}{13}$×$\frac{1}{2}$×13×$\frac{1}{8}$

答案： ($\frac{1}{3}$－$\frac{1}{4}$)÷25%
=($\frac{4}{12}$－$\frac{3}{12}$)÷0.25
=$\frac{1}{12}$÷$\frac{1}{4}$
=$\frac{1}{12}$×4
=$\frac{1}{3}$
($\frac{5}{7}$－$\frac{3}{14}$)÷45%
=($\frac{10}{14}$－$\frac{3}{14}$)÷0.45
=$\frac{7}{14}$÷$\frac{9}{20}$
=$\frac{1}{2}$×$\frac{20}{9}$
=$\frac{10}{9}$
25%×$\frac{3}{8}$＋75%÷$\frac{8}{3}$
=0.25×$\frac{3}{8}$＋0.75×$\frac{3}{8}$
=($0.25+0.75$)×$\frac{3}{8}$
=1×$\frac{3}{8}$
=$\frac{3}{8}$
60%×$\frac{5}{6}$＋4÷$\frac{8}{5}$
=0.6×$\frac{5}{6}$＋4×$\frac{5}{8}$
=0.5＋2.5
=3
$\frac{7}{8}$×$\frac{4}{21}$×$\frac{2}{3}$÷3
=$\frac{1}{6}$×$\frac{2}{3}$×$\frac{1}{3}$
=$\frac{1}{9}$×$\frac{1}{3}$
=$\frac{1}{27}$
$\frac{12}{5}$×($\frac{5}{6}$＋$\frac{3}{4}$)＋$\frac{1}{3}$
=$\frac{12}{5}$×$\frac{5}{6}$＋$\frac{12}{5}$×$\frac{3}{4}$＋$\frac{1}{3}$
=2＋$\frac{9}{5}$＋$\frac{1}{3}$
=2＋1$\frac{4}{5}$＋$\frac{1}{3}$
=3$\frac{12}{15}$＋$\frac{5}{15}$
=3$\frac{17}{15}$=4$\frac{2}{15}$
$\frac{3}{4}$×$\frac{1}{3}$＋$\frac{1}{4}$×$\frac{1}{3}$－$\frac{1}{3}$
=($\frac{3}{4}$＋$\frac{1}{4}$－1)×$\frac{1}{3}$
=(1－1)×$\frac{1}{3}$
=0
$\frac{5}{8}$×$\frac{4}{13}$×$\frac{1}{2}$÷5
=$\frac{5}{8}$×$\frac{4}{13}$×$\frac{1}{2}$×$\frac{1}{5}$
=$\frac{1}{52}$
$\frac{2}{13}$×$\frac{1}{2}$×13×$\frac{1}{8}$
=($\frac{2}{13}$×13)×($\frac{1}{2}$×$\frac{1}{8}$)
=2×$\frac{1}{16}$
=$\frac{1}{8}$