In solving Hannah's prayer request for a kid, God solved his own need for a prophet. Samuel was the fulfillment of Hannah's prayer request and who became the greatest prophet(fulfillment of God's need) of Isreal. So many times our prayer requests are delayed(appears to be delayed) and there is struggle for fulfillment of our prayer request because along with the fulfillment of our prayer request, God is fulfilling His own need along with it.