Toán Lớp 6: 10+11+12+13+….+99 tinh nhanh
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Toán Lớp 6: 10+11+12+13+….+99 tinh nhanh
Comments ( 2 )
= ( 99 + 10 ).[ ( 99 – 10 ) + 1 ]/2
= 109.90/2
= 109.45
= 4905