Estimate how many: tag, catch again and compare

Answer Key - Grade 7 Math Worksheet

Circle the best answer, or write your answer on the line.

1. 1.

   Ari tags 50 ladybugs in a garden. Later, 40 are caught and 8 have tags. About how many are there in all?

   250
2. 2.

   Bo marks 60 beans and mixes them into a big jar. A scoop of 48 beans has 12 marked ones. About how many are there in all?

   240
3. 3.

   Esme puts stickers on 30 turtles' shells. Later, 50 turtles are spotted and 5 have stickers (they look very proud). About how many are there in all?

   300
4. 4.

   Jun tagged 50 ladybugs; a later catch of 40 had 8 tagged. Which proportion finds the total N?

   • 8/40 = 50/N
   • 40/8 = 50/N
   • 8/50 = N/40
5. 5.

   Kira marked 60 beans; a scoop of 48 had 12 marked. Which proportion finds the jar's total N?

   • 12/48 = 60/N
   • 12/60 = 48/N
   • 48/12 = 60/N
6. 6.

   Noah tagged 30 fish in a class aquarium study, and half the next catch is tagged. About how many fish are there?

   • About 30
   • About 15
   • About 60
7. 7.

   In Pia's second catch, every turtle has a sticker. What does that suggest?

   • Stickers multiply
   • Nearly all were tagged already
   • The pond holds many more
8. 8.

   Ren adds 100 colored grains to a rice bag, mixes, and scoops 100 grains: 20 are colored. About how many grains are in the bag?

   • About 500
   • About 2,000
   • About 120
9. 9.

   Tala marks 30 marbles in a bag, mixes, and draws 20: 4 are marked. About how many marbles are in the bag?

   • About 150
   • About 54
   • About 24
10. 10.

    Why can Zee's bean-jar method also estimate fish in a lake?

    • Both are counted one by one
    • Both use a marked share
    • Beans and fish weigh the same