tìm a và b
a. a - 285 + 85 = 2495
b. 2748 - a + 8593 = 10495
c. b : 7 x 34 = 8704
d. 85 x b : 11 = 425
e. [ a - 4737 ] : x = 5738 -943
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`@` `\text {Ans}`
`\downarrow`
`a)`
`2748 + x - 8593 = 10495`
`2748 + x = 10495 + 8593`
`2748 + x = 19088`
`x = 19088 - 2748`
`x = 16340`
`b)`
`8349 + x- 5993= 95902`
`8349 + x = 95902 + 5993`
`8349 + x = 101895`
`x = 101895 - 8349`
`x = 93546`
Bài 7:
a, \(x\) = \(\dfrac{1}{5}\) + \(\dfrac{2}{11}\)
\(x\) = \(\dfrac{11}{55}\) + \(\dfrac{10}{55}\)
\(x=\dfrac{21}{55}\)
b, \(\dfrac{x}{15}\) = \(\dfrac{3}{5}\) - \(\dfrac{2}{3}\)
\(\dfrac{x}{15}\) = \(\dfrac{9}{15}\) - \(\dfrac{10}{15}\)
\(\dfrac{x}{15}\) = \(\dfrac{1}{15}\)
\(x\) = 1
c, \(\dfrac{11}{8}\) + \(\dfrac{13}{6}\)= \(\dfrac{85}{x}\)
\(\dfrac{33}{24}\) + \(\dfrac{52}{24}\) = \(\dfrac{85}{x}\)
\(\dfrac{85}{24}\) = \(\dfrac{85}{x}\)
24 = \(x\)
\(A=\frac{34}{7.13}+\frac{51}{13.22}+\frac{85}{22.37}+\frac{68}{37.49}\)
\(=\frac{17.2}{7.13}+\frac{17.3}{13.22}+\frac{17.5}{22.37}+\frac{17.4}{37.49}\)
\(=17\left(\frac{2}{7.13}+\frac{3}{13.22}+\frac{5}{22.37}+\frac{4}{37.49}\right)\)
\(=\frac{17}{3}\left(\frac{6}{7.13}+\frac{9}{13.22}+\frac{15}{22.37}+\frac{12}{37.49}\right)\)
\(=\frac{17}{3}\left(\frac{1}{7}-\frac{1}{13}+\frac{1}{13}-\frac{1}{22}+...+\frac{1}{37}-\frac{1}{49}\right)\)
\(=\frac{17}{3}\left(\frac{1}{7}-\frac{1}{49}\right)\)\(=\frac{17}{3}.\frac{6}{49}=\frac{17.2}{49}=\frac{34}{49}\)
Có : \(\frac{17}{24}=\frac{34}{48}\)
Vì 48 < 49 => \(\frac{34}{48}>\frac{34}{49}\). Hay \(\frac{17}{24}>A\)
Mỗi câu đúng được 0,75 điểm
a) x × 7 + 85 = 106
x × 7 = 106 – 85
x × 7 = 21
x = 21 : 7
x = 3
b) x : 9 + 72 = 137
x : 9 = 137 - 72
x : 9 = 65
x = 65 x 9
x = 585
a.
a-285+85=2495
=>a=2495+285-85
=>a=2695
b.
2748 - a + 8593 = 10495
=>11341-a=10495
=>a=11341-10495
=>a=846
c.
b:7xx34=8704
=>b:7=256
=>b=1792
d.
85 x b : 11 = 425
=>b:11=5
=>b=55
a.
a-285+85=2495
=>a=2495+285-85
=>a=2695
b.
2748 - a + 8593 = 10495
=>11341-a=10495
=>a=11341-10495
=>a=846
c.
b:7xx34=8704
=>b:7=256
=>b=1792
d.
85 x b : 11 = 425
=>b:11=5
=>b=55