小學奧數2問

1) 111111011 x 111111211
= ( 1111111 - 100)(1111111 + 100)
= 1111111^2 - 100^2
= 12345678987644321

2) 2/3 + 2/24 + 2/24 + 2/84 + 2/63 + 2/180 + 2/120 + 2/312 + 2/195 + 2/480
= 2/3 + 1/6 + 1/6 - 1/7 +1/7 - 1/9 + 1/9 - 1/10 + 1/10 - 1/12 + 1/12 - 1/13 +
1/13 - 1/15 + 1/15 - 1/16
= 1 - 1/16
= 15 /16

1)111111011 x 111111211 =1.2345679 × 1016=1 254.32099
2)2/3 + 2/24 + 2/24 + 2/84 + 2/63 + 2/180 + 2/120 + 2/312 + 2/195 + 2/480=0.9375

111,111,011 * 111,111,211 = 1.2345678987644e+16

(2 / 3) + (2 / 24) + (2 / 24) + (2 / 84) + (2 / 63) + (2 / 180) + (2 / 120) + (2 / 312) + (2 / 195) + (2 / 480) = 0.9375