a-b=4/5 hỏi a=?
a\(\div\)b =2/3 b=?
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DH
11 tháng 9 2016
a) 2a - 1, b + 3, 5 - 2c TLT với 2 , 3 , 4
=>\(\frac{2a-1}{2}=\frac{b+3}{3}=\frac{5-2c}{4}=k\left(kthuocZ\right)\)
=>a=2k+1,b=3k-3,c=(5-4k)/2
Thay vao a+b-c=2 tim duoc k, chu y k thuoc Z, tu do suy ra a,b,c.
b) Tuong tu.
TP
0
11 tháng 9 2016
Ta có:
\(\frac{A}{B}=\frac{3}{7}\); \(\frac{B}{C}=\frac{15}{28}\)
=> \(\frac{A}{B}.\frac{B}{C}=\frac{3}{7}.\frac{15}{28}\)
=> \(\frac{A}{C}=\frac{45}{196}\)
Vậy tỉ số của 2 số C và A là \(\frac{196}{45}\)
Chọn A
29 tháng 11 2018
a) Theo đề, ta có:
\(\frac{a}{2}=\frac{b}{3}=\frac{c}{5}\) và a + b + c =1,5
Theo t/c của dãy tỉ số bằng nhau:
\(\frac{a}{2}=\frac{b}{3}=\frac{c}{5}=\frac{a+b+c}{2+3+5}=\frac{1,5}{10}=\frac{3}{20}\)
=>a=0,3
b=0,45
c=0,75
29 tháng 11 2018
a) Vì a,b,c tỉ lệ với 2,3,5
=> \(\frac{a}{2}=\frac{b}{3}=\frac{c}{5}\)
Áp dụng t/c dãy tỉ số bằng nhau :
\(\frac{a}{2}=\frac{b}{3}=\frac{c}{5}=\frac{a+b+c}{2+3+5}=\frac{1,5}{10}=\frac{3}{20}\)
\(\frac{a}{2}=\frac{3}{20}=>a=\frac{3}{20}.2=\frac{3}{10}\)
\(\frac{b}{3}=\frac{3}{20}=>b=\frac{3}{20}.3=\frac{9}{20}\)
\(\frac{c}{5}=\frac{3}{20}=>c=\frac{3}{20}.5=\frac{3}{4}\)
b)
Áp dụng t/c dãy tỉ số bằng nhau :
\(\frac{a}{2}=\frac{b}{3}=\frac{c}{4}=\frac{a}{2}=\frac{2b}{6}=\frac{3c}{12}=\frac{a+2b-3c}{2+6-12}=\frac{-20}{-4}=5\)
\(\frac{a}{2}=5=>a=5.2=10\)
\(\frac{b}{3}=5=>b=5.3=15\)
\(\frac{c}{4}=5=>c=5.4=20\)
c) \(\frac{a}{2}=\frac{b}{3},\frac{b}{5}=\frac{c}{4}\)
\(\frac{a}{10}=\frac{b}{15},\frac{b}{15}=\frac{c}{12}\)
\(=>\frac{a}{10}=\frac{b}{15}=\frac{c}{12}\)
Áp dụng t/c dãy tỉ số bằng nhau
\(\frac{a}{10}=\frac{b}{15}=\frac{c}{12}=\frac{a+b-c}{10+15-12}=\frac{-39}{13}=-3\)
\(\frac{a}{10}=-3=>-3.10=-30\)
\(\frac{b}{15}=-3=>-3.15=-45\)
\(\frac{c}{12}=-3=>-3.12=-36\)
21 tháng 7 2016
Test 1Grammar 1 Complete the sentences with the verbs in bold.play do drive live listen1 I ____do___ my homework every evening.2 My cousins ____live___ in London.3 My Uncle Mike ____drive___ a bus.4 They ___play____ football at the weekend.5 We ___listen___ to music on the bus.2 Complete the sentences with the correct word.1 My dad ____gets up___ at 6.30 every morning.2 Ben ____studies___ very hard at school.3 We ___watch____ television after school.4 My cousin ____drives___ his car to work every day.5 I ___live___ in Leeds with my family.Vocabulary 3 Complete the sentences with the correct words.1 My _______ lives in America.A parents B teachers C cousin2 I’m _______. I stay in bed late every day!A intelligent B lazy C popular3 This film isn’t very interesting. It’s _______!A expensive B modern C boring4 That is my _______ new car.A parents B parent’s C parents’5 She’s got two _______.A babies B babys C baby’sTotal: ___ /15Test 2Grammar 1 Rewrite the sentences in the negative.1 I play football. ________________I don't play football_________________2 My cousin lives in this town. _______My cousin does live in this town _____3 My sister and I go to school by bike. _ My sister and I don't go to school by bike____4 Darren and Fiona study French. Darren and Fiona don't study French5 Pete likes school. Peter doesn't like school 2 Complete the sentences with the correct form of the verbs in the box.go shopping swim cook go like1 We ___go____ to school by bus. My mum drives us in her car.2 My dad ____cooks___ dinner on Thursday evenings because my mum plays tennis.3 I ___go shopping____ with my parents. I think it’s boring!4 Katy ___likes____ rap music very much.5 Gary ___swimming____ on Fridays. He does his homework at home. Everyday English3 Write questions for these answers.
1 _________How are you______________? Fine thanks.
2 __________How old are you_____________? I’m fifteen.
3 __________Where are you from_____________? London.
4 _________Have you got one brother_______? Yes, I’ve got one brother.
5 _______How old is he_______? He’s eighteen.
8 tháng 11 2016
ĐỌC ĐOẠN VĂN, TRẢ LỜI CÁC CÂU HỎI:1-What does Mrs Lien do ?Mrs Lien is a nurse.2-How many rooms does her house have ?There are five room in her house.3-Is the yard big or small ?The yard is small.4-Where are the flowers ?The flowers are to the left of the yard.5-What is there behind the house ?There is a well behind te house.Ex2: CHỌN TỪ THÍCH HỢP ĐIỀN VÀO CHỖ TRỐNG:I (1) __________ usually eat breakfast. I only have (2) __________ of coffee. I don’t eat (3)__________ until about eleven o’clock. Then I have a biscuit and a glass of (4) ___________. For lunch I usually have a salad. That’s (5) __________ about two o’clock. I have (6) __________ at haft past six in the afternoon. I’m a vegetarian, so I don’t eat (7) ___________ or fish. I eat cheese and eggs and thing like that. I have a glass of water or fruit (8)___________ with my meal.1/ A. don't B. not C. am not D. No2/ A. a packet B. a cup C. can D. a bar3/ A. any B. some C. any thing D. something4/ A. peas B. rice C. chocolates D. milk5/ A. at B. on C. in D. of6/ A. breakfast B. lunch C. dinner D. supper7/ A. meat B. rice C. vegetables D. noodles8/ A. water B. soda C. juice D. lemonade
\(a-b=\frac{4}{5}\)
\(\Rightarrow a=b+\frac{4}{5}\)
\(a:b=\frac{2}{3}\)
\(\Rightarrow b=a:\frac{2}{3}=\frac{3a}{2}\)
\(A-B=\frac{4}{5}\)
\(A=B+\frac{4}{5}\)
\(A:B=\frac{2}{3}\)
\(B=A:\frac{2}{3}=\frac{3A}{2}\)