You can measure 100 grams of cooked rice using a tablespoon.
You can calculate the estimate of 100 grams of cooked rice using a tablespoon as shown below;
1 tablespoon will be equivalent to 10 grams.
1 tablespoon of cooked rice = 10g of cooked rice. That is; 10g × 1 tbsp = 10 grams.
10 tablespoons of cooked rice = 100g of cooked rice. That is; 10g × 10 tbsp = 100 grams.
100 grams of uncooked can produce 300 grams of cooked rice.
Therefore it is possible to measure 100 grams of cooked rice without a scale.