Preguntas del examen de matemáticas de primaria 12 15 3
Primero, 239/12
Entonces 1/12+2/12+3/12+.
= (1+2+3.+239)/12 -(1+2+3.+19)
=((1+239)X239)/(2x 12)-((19+1)x 19)/2
=2390 - 190
=2200
2.3321 /20 ÷ 41 =(3321 / 41)/20= 81/20
3.(-1/3+7/12-9/211/30-13/42+15/56)×21
=-1/3+(3+4)/(3 x4)-(4+5)/(4x 5)+(5+6)/(5x 6)-(6+7)/(6x 7 )+(7+8)/(7x 8))×21
=(-1/3+(1/3+1/4)-(1/4+1/5)+( 1/5+1/6)-(1/6+1/7)+(1/7+1/8))×21
=21/8
= 2.625