Toán Lớp 5: tìm x:
a, 7/x =3/12
b, x+x .1/4:2/7+x:2/9=255
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Toán Lớp 5: tìm x:
a, 7/x =3/12
b, x+x .1/4:2/7+x:2/9=255
Comments ( 2 )
a. $\frac{7}{x}$ = $\frac{3}{12}$
=>$\frac{7}{x}$ = $\frac{1}{4}$
=> x = 7 x 4 : 1 =28
vậy : $\frac{7}{28}$ = $\frac{1}{4}$
=>$\frac{1}{4}$ = $\frac{1}{4}$
.
b. x+x . $\frac{1}{4}$ : $\frac{2}{7}$ + x : $\frac{2}{9}$= 255
x+x . $\frac{1}{4}$ . $\frac{7}{2}$+ x . $\frac{9}{2}$ = 255
x+x . $\frac{7}{8}$ + x . $\frac{9}{2}$ = 255
x . ( $\frac{7}{8}$ + $\frac{9}{2}$ + 1 ) = 255
x . ( $\frac{7}{8}$ + $\frac{36}{8}$ + $\frac{8}{8}$) = 255
x . $\frac{51}{8}$ = 255
x = 255 : $\frac{51}{8}$
x = 40
a, 7/x =3/12
7/x = 1/4 ⇒ 7.4 = x.1
7.4/x = x.1/x
7.4/x = 28 ( ý là 7 x 4 = 28 )
kết quả = 28
Chúc bn học tốt ặ!!