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Ta có sơ đồ:
Học sinh khối 5 /-----/-----/-----/-----/-----/-----/-----/-----/-----/
Học sinh khối 4 /-----/-----/-----/-----/-----/-----/-----/
Giá trị 1 phần là:
64 : (9 - 7) = 32 (học sinh)
Học sinh khối 5 là:
32 x 9 = 288 (học sinh)
Đáp số: 288 học sinh
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\(\frac{2}{3}=\frac{12}{18};\frac{3}{4}=\frac{12}{16};\frac{4}{5}=\frac{12}{15}\)
Vậy ta có thể nói: biết rằng \(\frac{12}{18}\)số hs giỏi khối 3 bằng \(\frac{12}{16}\)số hs khối 4 và bằng \(\frac{12}{15}\)số hs khối 5.
Ta có sơ đồ:khối 3: 18 phần
khối 4:16 phần
khối 5: 15 phần
tổng số phần:18+16+15=49(phần)
số hs giỏi khối 3: 147:49x18=54(hs)
số hs giỏi khối 4: 147:49x16=48(hs)
số hs giỏi khối 5: 147:49x15=45(hs)
vậy:...
hok tốt
Vì 2/3 số HSG khối 3 =3/4 số HSG= 4/5 số HSG khối 5
--> 12/18 số HSG khối 3= 12/16 số HSG khối 4= 12/15 số HSG khối 5
--> 1/18 số HSG khối 3= 1/16 số HSG khối 4= 1/15 số HSG khối 5
Từ đó , ta có hình vẽ:
Tổng số phần bằng nhau là :
18 + 16 +15= 49 ( phần bằng nhau)
--> Khối 3 có số HSG là :
147: 49x 18= 54 ( HSG)
--> Khối 4 có số HSG là :
147 :49 x 16= 48 ( HSG)
--> Khối 5 có số học sinh là :
147 - 48 -54 = 45 ( HSG)
Vậy khối 3 có 54 HSG
khối 4 có 48 HSG
khối 5 có 45 HSG
Số học sinh khối 4 là :
25 : ( 5 - 4 ) x 5 = 125 ( hs )
Số học sinh khối 5 là :
125 : 5 x 4 = 100 ( hs )
Giải
Khối 4 có số học sinh là :
25 : ( 5 - 4 ) * 5 = 125 ( h/s )
Khối 5 có số học sinh là :
125 : 5 * 4 = 100 ( h/s )
Đáp số : khối 4 : 125 h/s
khối 5 : 100 h/s