Tính nhanh
21.72_11.72+9o.72+49.125.16
Tính nhanh:
49.125.16
49 . 125 . 16
= 49 . (125 . 16)
= 49 . 2000
= 98000
Câu 1(2,0 điểm): Tính hợp lí:
a) 21.7² - 11.7² + 90.7² + 49.125.16
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a,21.7^2-11.7^2+90.7^2+49.125.16
=7^2.(21-11+90)+49.(2.125.8)
=49.100+49.2000
=49.(100+2000)
=49.2100
=102900
tính nhanh : 21.72-11.72+90.72+49.125.16
21.72-11.72+90.72+49.125.16
=21.49-11.49+90.49+49.2000
=(21-11+90+2000).49
=2100.49
=102900
21.72-11.72+90.72+49.125.16
=21.49-11.49+90.49+49.2000
=(21-11+90+2000).49
=2100.49
=102900
Tính nhanh
21.72-11.72+90.72+49.125.16
Tính nhanh:
21.72-11.72+90.72+49.125.16
tính nhanh
21.72-11.72+90.72+49.125.16
21.72-11.72+90.72+49.125.16
=21.72-11.72+90.72+72.2000
=(21-11+90+2000).72
=2100.49
=102900
TÍNH NHANH
a, 35.34+35.86+65.75+65.45
b, 21.72-11.72+90.72+49.125.16
A,35*34+35*86+65*75+65*45
=35*[34+86]+65*[75+45]
=35*100+65*120
=35*100+65*100+65*20
=[35+65]*100+65*20
=10000+1300=11300
Tính nhanh
a, 35.34+35.86+65.75+65.45
b, 21.72-11.72+90+72+49.125.16
a) 35× 34 +35× 86 + 65 × 75 + 65× 45
= 35× ( 34+86) + 65× (75 + 45)
= 35× 120 + 65 × 120
= 120 × ( 35 + 65)
= 120 × 100 = 12000
Bài 3
a) 21.72-11.72+90.72+49.125.16
a) 21.72-11.72+90.72+49.125.16
=21.72-11.72+90.72+72.2000
=72.(21-11+90+2000)
=72.2100
=49.2100
=102900
a) \(21\cdot7^2-11\cdot7^2+90\cdot7^2+7^2\cdot125\cdot16=7^2\cdot\left(21-11+90+125\cdot16\right)=7^2\cdot2100=102900\)
\(21.7^2-11.7^2+90.7^2+49.125.16\)
=\(21.7^2-11.7^2+90.7^2+7^2.2000\)
=\(7^2.\left(21-11+90+2000\right)\)
=\(7^2.2100\)
=\(102900\)