. Thirty students from the Netherlands set up a record of 1,500,000 dominoes Of these, 1,138,101 were
toppled by one push. Which is a more reasonable
estimate for how many dominoes remained
standing after that push: 350,000 or 400,000?

How to do this , and can some one explain

Find the area of the regular hexagon if a side is 20 cm.

Statements reasons 1. ab ? cd; ad ? bc 1. given 2. ac ? ac 2. reflexive property 3. ? adc ? ? cba 3. ? 4. ? dac ? ? bca; ? acd ? ? cab 4. cpctc 5. ? dac and ? bca are alt. int. ? s; ? acd and ? cab are alt. int. ? s 5. definition of alternate interior angles 6. ab ? cd; ad ? bc 6. converse of the alternate interior angles theorem 7. abcd is a parallelogram 7. definition of parallelogram what is the missing reason in step 3?