Mathematical olympiad in the third grade of primary school: quick calculation and clever calculation

[b]

1. Calculate the following problems in a simple way.

① 17× 100

② 1 1 12×5

③23×9

④23×99

⑤ 12345× 1 1

⑥56789× 1 1

⑦36× 15

⑧ 123×25×4

⑨456×2× 125×25×5×4×8

⑩25×32× 125

( 1 1)3600÷25

answer

situation

① 17× 100= 1700

② 1 1 12×5=5560

③23×9=230-23=207

④23×99=2300-23=2277

⑤ 12345× 1 1= 135795

⑥56789× 1 1=624679

⑦36× 15=(36+ 18)× 10=540

⑧ 123×25×4= 123×(25×4)= 12300

⑨456×2× 125×25×5×4×8

=456×(2×5)×(25×4)×( 125×8)

=456000000

⑩25×32× 125

=(25×4)×( 125×8)

= 100000

( 1 1)3600÷25

=36× 100÷25

=36×4

= 144

upgrade

[b] 1。 Calculate the following question in a simple way. [b]

1.( 1) 12×4×25; (2) 125× 13×8; (3) 125×56; (4)25×32× 125。

2.( 1) 125×(80+4); (2)( 100-8)×25; (3) 180× 125; (4) 125×88。

3.( 1) 1375÷25; (2) 12880÷230。

4.( 1)( 128+ 1088)÷8;

(2)( 1040-324-528)÷4;

(3) 1 125÷ 125;

(4)4505÷ 17÷5。

5.( 1)384× 12÷8;

(2)2352÷(7×8);

(3) 1200×(4÷ 12);

(4) 1250÷( 10÷8);

(5)2250÷75÷3;

(6)636×35÷7;

(7)( 126×56)÷(7× 18)。

answer

situation

1.( 1) 1200; (2) 13000; (3)7000; (4) 100000。

2.( 1) 10500; (2)2300; (3)22500; (4) 1 1000。

3.( 1)55; (2)56。

4.( 1) 152; (2)47; (3)9; (4)53。

5.( 1)576; (2)42; (3)400; (4) 1000;

(5) 10; (6)3 180; (7)56。