a/ 48 + 25 – 38 = 73 – 38 = 35

b/ 100 - 38 + 15 = 62 + 15 = 77

a. (83+234)-(34-17)

= (243-34)-(83+17)

= 200-100

= 100

B.(-15)+13+15.(36-25)

= (-15)+15.13+11

= 13+11

= 24

a) 25 < y - 15 < 26

=> 25  - 15 < y - 15 < 26 - 15

=> 10 < y < 11

=> \(x\in\left\{10,1;10,2;10,3;10,4;10,5;10,6;10,7;10,8;10,9\right\}\)

b) 64 > y + 35 > 62

=> 64 + 35 > y + 35 > 62 + 35

=> 99 > y > 97

=> y = 98

Vậy y = 98

B,. 64 > y + 35 > 62

<=>y+35=63

<=>y=63-35=28

Vậy y=28

\(\dfrac{24}{35}:\dfrac{15}{7}=\dfrac{24}{35}\times\dfrac{7}{15}=\dfrac{8}{25}\)

\(\Rightarrow chọn\) \(B\)

`# \text {DNamNgV}`

\(\dfrac{24}{35} \div \dfrac{15}{7} \\ = \dfrac{24}{35} \times \dfrac{7}{15} \\ = \dfrac{8}{25}\)

Chọn đáp án B.

Ta có: \(\frac{15}{16}\times\frac{24}{25}\times\ldots\times\frac{9999}{10000}\)

\(=\left(1-\frac{1}{16}\right)\times\left(1-\frac{1}{25}\right)\times\ldots\times\left(1-\frac{1}{10000}\right)\)

\(=\left(1-\frac14\right)\times\left(1-\frac15\right)\times\ldots\times\left(1-\frac{1}{100}\right)\times\left(1+\frac14\right)\times\left(1+\frac15\right)\times\ldots\times\left(1+\frac{1}{100}\right)\)

\(=\frac34\times\frac45\times\ldots\times\frac{99}{100}\times\frac54\times\frac65\times\ldots\times\frac{101}{100}\)

\(=\frac{3}{100}\times\frac{101}{4}=\frac{303}{400}\)

\(S6=15+17+19+21+...+151+153+155\)

Số các số hạng là:

\(\left(155-15\right):2+1=71\)

Vậy \(S6=\dfrac{\left(155+15\right).71}{2}=6035\)

\(S7=15+25+35+...+115\)

Số các số hạng là:

\(\left(115-15\right):10+1=11\)

Vậy \(S7=\dfrac{\left(115+15\right).11}{2}=715\)

\(S4=24+25+26+...+125+126\)

Số các số hạng là:

\(\left(126-24\right):1+1=103\)

Vậy \(S4=\dfrac{\left(126+24\right).103}{2}=7725\)