Short answers, pulled from the story.
Excavations at Harappa and Mohenjo-daro uncovered bricks with dimensions in a 4:2:1 ratio and standardized weights based on specific ratios. These weights equaled approximately 28 grams and were mass-produced in regular geometrical shapes such as hexahedra, barrels, cones, and cylinders.
The Śulba Sūtras list rules for constructing sacrificial fire altars during the Vedic period between 700 and 400 BCE. Baudhayana composed the best-known Sulba Sutra containing simple Pythagorean triples such as 3, 4, 5 and 5, 12, 13.
Aryabhata I calculated the value of π correct to four decimal places. He also defined sine as the modern relationship between half an angle and half a chord and provided tables listed values at 3.75° intervals from 0° to 90° with four decimal places accuracy.
Madhava of Sangamagrama founded the Kerala school of astronomy and mathematics in South India. It flourished between the 14th and 16th centuries with original discoveries ending around 1559-1632.
The decimal place-value system in use today was first recorded in India then transmitted to Islamic world and eventually to Europe. Earliest surviving evidence includes copper plate from Gujarat mentioning date 595 CE written in decimal notation though authenticity remains doubtful.